On Wikipedia:Preparing images for upload's talk page there is talk about this Category:Images with opaque backgrounds--E-Bod 04:21, 1 April 2006 (UTC)[reply]

It is so much simpler to merely go down the page to the "File history", click on "Upload a new version of this file", and upload the transparent image. There is then no need for: "After doing so, please replace all instances of this version..." since, as soon as the edit is done, all instances have already been replaced. GWFrog (talk) 21:54, 30 July 2015 (UTC)[reply]