My take on CFC57 using acetate or vellum is this card. Birthday's by the ton coming up this summer and I will get it off to someone, no doubt.
I am a big fan of using up "old stuff", and that's what I did with this card. I stuck 3 flower stickers from the Paper Studio onto a scrap of blue vellum, fussy cut them out, and colored the centers black. They looked fine blue, but I wanted to tie the card's touches of black all together. I found an MaMBI frame from about, oh, 2004 (!) and taped it onto the SU cardstock card base. Pop-dotted the flowers in the center, and added "Happy Birthday" from MFT's Birthday Princess set. I really like this concept. Hopefully, whoever gets this card will be doing the Happy Dance.