Board Thread:Support Requests - Designing Your Wiki/@comment-44721338-20200503112034

Hello, recently I just started a wiki. But since I'm a noob and don't know much, I decided to follow the instructions the wiki gave to me. then it told me to "customize" my theme. I wanted to add a custom background. I know it's supposed to be smaller than 300kb but nothing else. I have no idea what the size needs to be. I've checked the wiki help page, but i still couldn't find a size. Can someone tell me which size goes the best? 