You should look for some freeware illustrators online and if there are tutorial videos on youtube. Those videos are very informative and you can see, if you like the handling. Gimp is freeware, but I personally hate Gimp, I think it’s way too complicated.
I’m using picmonkey.com, but you have to pay for it.
If you want to create a coverpage with the Viki editor, you need some basic html skills, there are tutorials online, too. So you should learn how to change the color of the background, to add a border with round or with edges for example. With the Viki editor you can add photos easily, you can add fonts and change them, change the color of the font, you can add hyperlinks.
If you want to create a coverpage which you don’t need to change afterwards, you can upload this “photo” with freeware online like directupload.com Just ask google I’m using abload.de but this is a German site. You have to copy the URL and add it to the Viki editor.
If you want to create a fancy coverpage, but still need to add the team, you can upload the fancy one and a simple background, too and combine both. If you add them both to the Viki editor you will have a really small space between them, but I don’t mind this. My HTML skills are kind of limited so I can’t help with tables, gifs and CCS.
And if you want to see some of my coverpages, this is my profile, you just need to click on the “German Coverpage” (these are hyperlinks") and can see the respective ones https://www.viki.com/users/somejuwels/about