For icons just do a search on google for icon libraries. Some are free and some others are cheap for what you get.

Do not pay for custom icon design unless you absolutely need to.

For site design your best bet is to look at CSS galleries. Tons of designers put their portfolios up there.

Also check out deviantart.com for a huge selection of freelance art.

Be forwarned that good designers are usually very busy and/or very expensive. A lot of overseas designers are pretty decent and a little cheaper (Asia/Eastern Europe). In 10 years as a programmer Ive had better luck finding top coders than top designers.