I'm a bit new on this site but as far as I could search, I didn't find a solid place on this kind of work, so I'd be glad if someone showed me a bit about how to do them.

Thanks in advance

Welcome! For manip advice, we have a thread full of tutorials, including stuff on empty eyes and other effects <<hypnohub.net/forum/show/2317?page=2|here.>> Hope that helps!

In case you need to see how it is done, rather than seeing just pictures or text descriptions, I made a video tutorial on some basic empty eyes using paint.net. And then it took like 3 hours to upload. Stupid slow internet..

www.youtube.com/watch?v=h...=UUjOrSL3Mhkl9dEORWpzC4Bg

Mine is probably a simpler style than PomPom's since it doesn't involve drawing a whole new eye. ^_^; PomPom's is probably better if the source is too small to work with without pixelation.