pahansen
Fish Fanatic
I will speak to the issue of "how many plants", since I don't think I'm qualified to answer anything else. 
I assume you are using plastic or silk plants, as opposed to live plants. This is just from the looks of your tank -- perhaps you have a combination of both types. Nothing wrong with any of that. Assuming your plants are not live, there is no real limit on how many you use. Of course, adding more plants will be more expensive, so that part depends upon you. And at some point, the volume of your plants could start to take away from the volume of water left for your fish to swim in, but I assume you're not thinking of adding that many plants!
My guess is that you are not quite happy with your "aquascaping" -- you might not really like the way your plants are set up, but you're not sure why.
Here is my suggestion -- start looking at planted tanks (people who keep live plants with their fish) and find out what you like. You can start by looking at the Member's Aquarium and Fish Pictures board on TFF or you can just look up "planted tanks" on Google. After looking for a while, you'll certainly get an idea of what you, personally, find aesthetically pleasing.
For example, I love the look of live plants and don't mind the upkeep, so that is what I have. But I don't care for the heavily planted tanks that some people have. (I can appreciate them, and the work that goes into them, but they just don't ring my bells.) I also didn't care for the sparse look, or the single specimen look (just one or two kinds of plants in abundance). But eventually I found a style of planting that I did like, and that's how my tank is planted now. Basically, if you look at enough pictures, you'll find your niche.
The other thing that looking at planted tanks will do is that it will give you an idea of the way plants will naturally grow when left alone in a tank. Does this plant stay spindly and grow taller? Will it branch and become very full? Will it spread from the root system and start to fill a corner of the tank? Knowing these things will help you to replicate that look in your own tank. Once you know what you want your tank to look like, you can try to re-create that look in your own aquarium with silk or plastic plants. Making a "fake" plant look real may require you to bunch two or three silk or plastic plants (of the same type) together, but you will be much happier with the result.
Finally, I will say that most aquatic plants (live) are considered to be either foreground, midground, or background plants. This has a lot to do with how tall (and sometimes how full) they will be. Following these guidelines will help you to have a more pleasing tank as well -- taller plants in the back/center, shorter along the front/sides. Also, there are "specimen" plants -- plants that are used as a feature piece, perhaps in the center of the tank, because they are particularly large, attractive, or just plain cool. The Madagascar Lace Plant is a good example of this. You might want to try that as well.
Just some thoughts about "planting" without live plants. I really do think you can have it all nowadays -- the silk and plastic plants can look surprisingly real, and require far less care than most live plants.
Good luck,
Pamela
PS -- I personally like to have something taller in front of my filter intake and heater, just so people notice the plant rather than the hardware. Just a tip -- take it or leave it.
I assume you are using plastic or silk plants, as opposed to live plants. This is just from the looks of your tank -- perhaps you have a combination of both types. Nothing wrong with any of that. Assuming your plants are not live, there is no real limit on how many you use. Of course, adding more plants will be more expensive, so that part depends upon you. And at some point, the volume of your plants could start to take away from the volume of water left for your fish to swim in, but I assume you're not thinking of adding that many plants!
My guess is that you are not quite happy with your "aquascaping" -- you might not really like the way your plants are set up, but you're not sure why.
Here is my suggestion -- start looking at planted tanks (people who keep live plants with their fish) and find out what you like. You can start by looking at the Member's Aquarium and Fish Pictures board on TFF or you can just look up "planted tanks" on Google. After looking for a while, you'll certainly get an idea of what you, personally, find aesthetically pleasing.
For example, I love the look of live plants and don't mind the upkeep, so that is what I have. But I don't care for the heavily planted tanks that some people have. (I can appreciate them, and the work that goes into them, but they just don't ring my bells.) I also didn't care for the sparse look, or the single specimen look (just one or two kinds of plants in abundance). But eventually I found a style of planting that I did like, and that's how my tank is planted now. Basically, if you look at enough pictures, you'll find your niche.
The other thing that looking at planted tanks will do is that it will give you an idea of the way plants will naturally grow when left alone in a tank. Does this plant stay spindly and grow taller? Will it branch and become very full? Will it spread from the root system and start to fill a corner of the tank? Knowing these things will help you to replicate that look in your own tank. Once you know what you want your tank to look like, you can try to re-create that look in your own aquarium with silk or plastic plants. Making a "fake" plant look real may require you to bunch two or three silk or plastic plants (of the same type) together, but you will be much happier with the result.
Finally, I will say that most aquatic plants (live) are considered to be either foreground, midground, or background plants. This has a lot to do with how tall (and sometimes how full) they will be. Following these guidelines will help you to have a more pleasing tank as well -- taller plants in the back/center, shorter along the front/sides. Also, there are "specimen" plants -- plants that are used as a feature piece, perhaps in the center of the tank, because they are particularly large, attractive, or just plain cool. The Madagascar Lace Plant is a good example of this. You might want to try that as well.
Just some thoughts about "planting" without live plants. I really do think you can have it all nowadays -- the silk and plastic plants can look surprisingly real, and require far less care than most live plants.
Good luck,
Pamela
PS -- I personally like to have something taller in front of my filter intake and heater, just so people notice the plant rather than the hardware. Just a tip -- take it or leave it.
He really enjoyed it, but I couldn't afford to buy new sword plants twice a week!
