Brilliant handkerchief invites by printing custom fabric with a square map design at Spoonflower and then cutting up the fabric to make handkerchiefs.
I've always really liked clean line drawings, like Danny Gregory's. Every so often I try to get into sketchbook journaling because I'd like to be able to document surroundings like this (Oh So Beautiful Paper)
Amazing laser cut gatefold, closed with a wax seal by Paisley Quill, via Oh So Beautiful Paper. I think this could be translated to a really cool design with red Chinese papercuts. Which I've totally posted about before, heh.
Envelope template from Melissa of IS•LY
Also not a specific design but something that may be useful: design*sponge's favorite fonts roundup.