User blog comment:X-Machinist-X/Dishonored random stuff/@comment-26438896-20151030165752/@comment-26438896-20151030171813

Before uploading my last images I read here :

"What file types are allowed on Wikia?
By default, file types that can be uploaded are .png, .gif, .jpg, .jpeg, .ico, .pdf, .svg, .odt, .ods, .odp, .odg, .odc, .odf, .odi, .odm, .ogg, .ogv, and .oga. Some wikias may allow additional file types on request."

And yes, PNG has a good quality, but I don't think it's strictly necessary for a screenshot.