Admittedly, the Toad may be going out on a tiny tree limb here by recommending you buy art for others. Art is, after all, a purely subjective thing. What you may hang on your wall might be deemed simply hideous by your friend, not even suitable as California basement decor.
Still, I feel compelled to mention this wonderful art site, 20X200, partially because it really does feature a variety of art, much of which is very nice. Fine, maybe not the first choice on a major curator's list, but still looks good on a wall. And some of the pieces are by emerging artists, so a photograph picked up today might be the masterpiece of tomorrow. Here's how the site works: every piece is limited edition (so when it's sold out, it's sold out forever), and each piece comes in three different sizes, ranging in price from $20(!) to $2000. That means you can have the giraffe above (which looks much like more expensive renditions of this theme I've spotted in books and magazines) for anywhere from $20 for a small print to $200 for a larger one... you get my drift.
I'm also recommending 20x200 because I've read a lot of really snotty comments out there recently regarding art, and it annoys. Art should be for everyone, not just the over educated and anointed few. So there.