This diy project is simple enough with all different sizes of envelopes glued on the pages of an album for people to fill with little notes of well wishes and advice. It would be so fun for the couple to go through it after the wedding!
This Bride had cut out squares of fabric, and guests wrote notes on them (with the fabric pens to avoid bleeding on the fabric), she later had them turned into a quilt! Such a nice keepsake. Use fabrics that would work with your home decor so you could have it out on display!