Harry Potter Wedding

On amazon, there are candle stick lights that use a wand to remote control them, they also have strings attached to make them "float" when hanging from the ceiling. It would be about $20 for a 12 pack and there are diffferent sized tapers. For a couple hundred bucks depending on the size of the venue you could get the feel of the dining hall with the candles.

I would also look at photo backdrops for different scenes from harry potter that could match for wall decor. They don't have to be attached to walls as you can have the floral backdrop stands to hold up the backdrops.

For center pieces, you can do the clear cylinders with lights inside with orbeez and water... thing it looks a bit magical just having lights in water.

you of course can do garlands with lights woven into them... that can be pretty inexpensive depending on how you do it, but is also relatively easy to do DIY to make that cheaper.

For a photobooth, you can make all the accessories harry potter themed pretty easily as well

For favors, you can do the jelly beans, maybe not the trixter gross ones though!)

just some ideas... I hope this helps!