Forum:Image replacement

Hello. I'm looking to change the image of this wiki page: Eridian Splat Gun

I have sadly run into a problem when doing so. The image I've wanted to replace it with uses the file type .png which can be found here, however I could not figure out a way to actually replace the image on the wiki page itself. In the tab File History, if I pressed "Upload a new version of this file", it would stick to a .jpg file type, meaning that, when I upload it, it gives me an error because it is a different file type.

Is there a way to replace the image I have uploaded with one that already exists on a wiki page? By the way, the buttons Photo, Gallery and Video, don't seem to work for me, under the menu "Add features and media", which is usually on the right during editing.

Please let me know. Thank you.

-ugyuu