Proclaim your love in a HUGE way! (36" x 48" to be exact!)
I am a fan of the statement piece, the one thing in a room that catches everyone's eye first and that you cannot possibly miss. If you want to make a statement for Valentine's Day but don't want to break the bank, giant printable posters are a great option! (And super awesome, and I'm absolutely doing this for both my roommates and my man).
A couple years ago I even printed a giant poster from a photo of my cousin and her fiancé and threw it up on our living room wall pre-celebration and she loved it. I love how Jules (below) customized a photo of her and her husband and made it into a statement piece above their bed.
If you want to make it a permanent piece in your home, Jules' tutorial above is a great option. Otherwise, if you just want an easy decoration for Valentine's Day, you can print out the poster and perhaps make some heart garland to hang with it, put confetti everywhere, buy flowers for the table, and/or bake up something delicious for your loved one to come home to.