I used a combination of things to create our Valentine's mantel.
First off, I bought some pre-cut foam hearts from JoAnn Fabrics and Crafts at 40% off. I think that made them $3 and some change. Caleb separated the solid hearts from the heart outlines, then he ordered them in his own little pattern. I glued them to a length of yarn and taped them to the mantel.
Second, I printed vintage Valentine's cards from the internet. I just Googled "vintage valentine's cards" and picket out some that I liked. I printed them on regular copy paper and cut them out. I used pink and red cardstock to create "mats" for them according to the sizes that I needed. The heart in the white frame is just a piece of printed scrapbook paper cut into a heart and taped to a piece of paper.
Finally, I pulled my red mosaic candles (from Kohl's) back out from the Christmas mantel and presto! I was done.