It is a form of art. It's called graphic design... you see it on basically every magazine cover, movie poster, CD cover, book cover etc etc anywhere. Arguably, it's one of the most widespread contemporary art forms. I used to do a heck of a lot of graphic design myself... but not so much lately. I need to get back into it... I miss it. Your pieces are pretty good, mandaleacalico!
Here's a few my sister and I have done in the past:
If anyone wants to see the whole collection (along with some random things thrown in that you should ignore). The link is here: Pictures by Eolith - Photobucket