Board Thread:Support Requests - Getting Technical/@comment-24385299-20140401003555/@comment-1330470-20140401010227

Wikis can only accept certain kinds of file extensions. You can upload a JPG but not an EXE - the latter might be a severe security risk. The default permitted file types on a new wiki are:

png, gif, jpg, jpeg, ico, pdf, svg, odt, ods, odp, odg, odc, odf, odi, odm, ogg, ogv, oga.

Some wikis may have customized the list of permissible file types: for example, you can upload a PSD to Community Central. The list of permissible file types for a wiki can be seen at Special:Upload on the wiki in question.

However, uploading a PSD is probably a poor choice. PSD images are very customized for use in Photoshop, and are likely to not be displayable on Wikia. This is because even if you upload a file, there is no guarantee that Wikia will know what to do with it. I ran into this problem when I enabled TGA on wolfenstein. I could upload them fine, but they could not be displayed on pages like a JPG. They could only be downloaded.

Your best bet is to export the image to JPG or PNG which will be permissible formats. If you understand the likely limitations but must upload the image as PSD, to preserve layers perhaps, then use Special:Contact to have PSD upload enabled.