I agree with the others.. nothing makes a betta's colors POP like a natural green background (and maybe some driftwood). IME the resin ornaments don't last forever.. eventually the paint starts to come off.. the walmart stuff goes bad especially fast. Plants last forever (if you take good care of them)
I defiantly agree with looking with looking through the betta home picture thread. Personally I'm a big fan of the glass vase gems and have two 10 gallons with gravel and gems and one 10 gallon with all gems. Its all about what you like and what you can afford! :)
I love fun bright themes with lots of gems and colours in smaller tanks, but natural looks best IMO in tanks 5 gallons and up. So, live plants, river stones, drift wood, natural gravel, and maybe a neutral coloured stone building of some sort.
I also like the whole "zen" type aquariums too, like this: