I'm very picky about the artwork in my house (size, color, style, etc), so I use Art.com . Zillions of things to choose from. It seems overwhelmingat first, but you can sort things by size, colors, style, etc. So when I wanted big, red, modern art for my living room, I just browsed through that stuff. Most is just poster quality, but when you frame it nicely no one can tell. Also they can put much of it onto a stretched-canvas-type look (my mother is considering this option for over her bed in earthquake-prone CA). There are usually some pretty good codes/coupons floating around.
I would say 90 percent of the non personal-photo art in our house came from that site or one other (allposter.com) like it.
For accessories I just keep my eyes open (and know measurements of spaces I'm looking to fill) at Target (great accent tables), Pier 1 Imports (big bamboo stuff), Cost Plus Imports, Z Gallerie, etc. A lot of my accessories come from trips or were given to me as gifts and I find somewhere to incorporate them.
PHXscuba