Okey, this is really hard to find a good place for free linking. Fist of all you may try free hosting catalouges and directories (find them with google or another search engine). Also, try to find popular forums (games, interests related etc.) and post there. You can allways try to find pictures related sites like (photogalaries or something else). You need to search end use consumer for your service. Ask yourself: where can they be?