Wall vinyls, tacky? Where is a good place to print your own custom designs?

I was wondering how you guys feel about Wall Vinyls? Do you know a good affordable place that does large scale vinyl prints? I have white walls in my apartment with minimal shelves and pictures and I was thinking some custom wall vinyls could liven the place up. They are a bit pricey for the larger ones so I thought making my own design would be cheaper as well as more personal and fun. Where would be a good place to get them printed?