Can I use Beethoven's Violin Romance No. 2 as a processional?

Heck, you can go down the aisle to Linkin Park if you really wanted to (and your venue would let you). It totally depends on what kind of wedding you will have. Experiment with other instruments, such as flutes, guitars (clical guitar is beautiful), harps, bagpipes if you're into them, or cultural music. Try checking out your heritage and then typing in "(Irish, African, Italian, Russian, etc) wedding music". You might get something really cool that way. Look for something with a good tempo so you aren't walking crazy slow or jogging down the aisle to keep time.