A NICE set of White fluffy towels are always a nice gift. You can never have too many.
Great quality bed sheets in white, off white or a fun color.
A digital picture frame is nice too, you can never have too many.
Scrapbooking sets! Everyone likes scrapbooking. I would suggest finding someone who sells it and in their catalog, they usually have an entire set with everything you need for like $20. Or a scrapbooking store, party supply or craft store should have the same.
Cocktail glasses / shot glasses / anything to do with bar or drink prep. Alcohol is cool too if they drink. Bottle of Patron, a good 2001 wine, Japanese Saki, etc.
Do they have a fav sports team? I've bought nice throw blankets with their team logo on it.
You could get them some sort of membership, something simple like Netflix, amusement park passes, etc.
Something from my gift wish list is the Dean & Deluca test tube spice rack . . . AWESOME!!
If you are on a budget, make a themed basket. Target has great stuff Wedding themed from picture frames to breath mints. Massage oils, romantic comedies, candles, journals, etc.
If they are young and children are in their future, maybe something cute to symbolize baby, if they are both 49ers fans, buy a cute onesie with their team on it. or whatever.
If you know the couple well, you could create a video presentation of their lives together, pics of ow they met set to romantic music (probably more for wedding party)