Tips for decorating a room divider?

I’d look at some uplighting - it’s pretty easy, shouldn’t be expensive but it looks good.

I agree with this or string lights.

You could string vertical fairy lights across it.

Depending on how the tables are set up for the event, you could do either uplighting or string lights and then hang photos of your and your future spouse from different stages of your relationship. That would be a nice, sentimental touch.