Go ONLINE. Try Art.com.....search by a theme, by color, by anything......

Two more:

http://www.gallerydirect.com/

http://www.greatbigcanvas.com/

Blue Stone Photography

Fine art prints, canvas prints, metal prints, wall displays and poster prints.

Supporting local new artists is always the best thing. You'd be surprised how many will make names for themselves later.

If you want decorative wall art, meaning inexpensive prints, the online retailers are great, some of them let you frame them online as well.

If however, you want "art," meaning original works, go to a gallery. All of the major cities and many smaller ones will have galleries where local artists show their work.