More and more of the free hosting sites are shutting off the ability to "hotlink" to images stored there. With the free sites, the only way they make money is with the ads that they put on the web pages. Linking to individual images from those sites uses up bandwidth (which is $) but doesn't give them the opportunity to display their ads.
You might check with your ISP and see if you have any web space available to you through them. Most ISPs give you some free webspace.