Pics?
Can give better advice if we can see it.
I've never had used decor, only second hand tanks, but I'd also likely bleach dip anything fake, rinsing well then soaking in triple dosed declorinator, before rinsing again and allowing to thoroughly air dry, to be sure every trace of bleach is gone. Over the top cautious, but I'd be wary of bacteria or worm eggs or something from a previous tank, but that's not really an issue if the decor hasn't been used in a long time and is all dried out. A good scrub to remove dust and old algae is probably all they really need.
I wouldn't bleach anything that's real stone or wood, ever. Boil or bake.
Anything fake that's painted - feel it for rough edges in hollows etc that might injure fish, rough edges can usually be sanded off. Be wary of anything with bubbling or flaking paint, since some paints are toxic and could leech chemicals into the water column.
If you keep shrimp or snails, pr plan to, you also need to be aware of potential medication traces that the decor may be contaminated with. Some meds contain copper, which can leave enough copper on second hand tanks and decor to kill inverts in a second hand tank. If you don't keep or plan to keep inverts, then not a problem. If you do, or want to, then Seachem has a product called Cuprisorb that you can run in the filter for a while to remove traces of copper.
All of the above are unlikely to happen, besides maybe the med poisoning thing, since a lot of people are quick to throw meds into their tank the minute something goes wrong, and aren't aware of copper traces being left behind. But, you did ask if there was anything else! So, all the things I'd bear in mind when buying second hand tank stuff.
