It may sound like water poured on the parade,but,personally,I don't like deco (peddle,plastic objects....) on the Betta tank. The tank does look pretty,but it is hard to cure and maintain the water quality once mishap does happen.
well items like glass should be fine - as they hold no paints / dyes that may affect the tank.
Well actually a LOT of colored glas is actually just painted. (Talking about the see through stuff)You'll want to test any colored see thorugh glass or otherwise by leaving it in a bucket of water for a few days or a week. If any of the color scratches off after a while then it's no good. =[
I know this because I've been looking for way to make tumbled glass for my own tank and on a tumbled glass forum someone bought a blue piece of glass to tumble and it ended up being regular clear glass with a blue see-though coating fired on. =[ She spent a ton of time on that batch too. =[
So just make sure to be careful! =] Oh! And you should look into tumbled glass! It's beautiful! <3