I just search and it's luck if I find really good ones :( ..And, I do like spending quite a lot of time now and again search for pics D: Some people seem to know good artist's actual websites, but I just find them searching the usual sites D:
Photobucket can be OK, but they're just other people's stuff posted up, and there can be a lot of screenshots there >_>
www.pixiv.net which is like the Japanese version of Deviantart can be good, and it's where most of the good pics come from, you just have to hunt for them. I think both Ruby and Azumi use it at times, too. Although there can be the usual bad art, you'll find the occasional amazing fanart there more easily than Deviantart. But you have to sign up to be able to see a full version of the things you search for, and all the tutorial's around haven't been updated since the site updated...so OK, I made one :P
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When you bookmark stuff, it gives otherer suggestions of what to look at, and they're usually good ones. Like, try adding this one to the site's bookmarks, and once click to confirm it, it'll come up with other suggestions
Some basic stuff to search for on there is Pokemon ポケモン or Pokemon Special manga pics ポケスペ and with the Pokemon one, you can find out the Japanese characters on Bulbapedia and paste that in along with Pokemon, like whatever the Japanese characters for Hikari are, stuff like that
I'd recommend stuff like Danbooru (which is English), but that either has really, really good pics (original source usually Pixiv), or horribly, horribly hardcore hentai o_o Yes, Pokemon stuff o.o So you can look there, but....it's your own fault if you're disturbed for life o.o And I really do mean that. So I don't go there often