I think it's time for you to get creative!!! Normally makes me feel better about it all! This can be in the form of new decorations, but make them yourself - check out the hardware and DIY section of the forum for ideas. I've just made some slate decorations in my new tank - great fun (probably more to do with the breaking up of the slate with a big 'ol hammer!)
You mentioned your plants keep floating away. Maybe try changing your substrate to something finer for them to root in. Sand perhaps, or just a fine gravel - which would be easier.
Failing that, new bits as well. When I upgraded my old tank from internal to external filter (had to do some royal bodging to get it in there!), it was like having a new tank all over again. I was surprised how much difference it makes asthetically, just by removing a small filter!
I hope this helps!