Board Thread:Support Requests - Designing Your Wiki/@comment-38546904-20190311225642/@comment-9605025-20190313195131

First, please note the edit to my previous post.

I suggest you read Help:Theme Designer and Help:Background. The approximate size depends on how you want it displayed. If you want to have it just once without a vertical line running though the center, it needs to be at least 2000px wide. As for the file size limit, you will need to compress the image.