I think you just save a gif you like (that is the right size for a cover) and just upload it like normal. Like the way that avatar gifs work. If you don't have one you can always just search into google images gif banners.
You can get access to the cover page of your profile by following the requirements. The requirements are 750 posts and 250 likes. If you match the requirements, you will follow the steps to come to have a profile cover. Step 1: Hover your forums username at the top bar and look for 'Preferences'. Then, click 'Preferences' You can see the step I did in the following screenshot: Step 2: After clicking 'Preferences', look down for the box called 'Use Profile Cover'. When you have found it, check the box for it to enable the cover page. You can see the step I did in the following screenshot: Step 3: After checking the box, go to your profile. You will see a big grey box appear in the top of your profile. If you hover over the box, you will see a 'Change cover' area. Hover that section, and go to 'Upload profile cover'. You can see the step I did in the following screenshot: Step 4: After clicking the section 'Upload profile cover', there will be a section below indicating 'Upload cover'. Make sure you have the picture or gif of your choice saved onto your computer before uploading the cover. Then, find the picture or gif of your choice and insert it. You can see the step I did in the following screenshot: Sorry about the images if it's hard to see. Hopefully this is helpful. Tell me if this is resolved, so it can be closed.
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