Usually, no — uploading an image to DeviantArt, Flickr, or similar sites does not automatically give you permission to use it on your own website. In general, the creator keeps the copyright unless they’ve explicitly licensed the image for reuse.

Check the image’s license or copyright information. Some images are shared under licenses such as Creative Commons, which may allow use if you follow the terms (for example, attribution, non-commercial use only, or no derivatives). If no license is clearly stated, assume you do not have permission.

Even if you credit the creator, that does not by itself make the use legal. Attribution only helps when the license specifically allows reuse with attribution.

If you want to use the image as a website background, the safest options are:

• use an image with a clear license permitting that use
• follow all license terms exactly
• or contact the creator and get permission

Also note that a site’s own terms may affect what users grant to the platform, but that usually does not mean third parties can reuse the image freely.