Board Thread:Support Requests - Getting Technical/@comment-26966924-20160827085255/@comment-24757753-20160827115215

> a) customize the special upload page to include some instructions from my side

No need for Staff help - just edit MediaWiki:Uploadtext page on the wiki to change the text on the Special:Upload page.

> b) if that doesn't work, is there maybe a button/widget for Special:Upload?

I don't know of any buttons or widgets, but if your file names are predictable, you could add a link in the template to upload an image. For example,  will give you a link to upload FileNameHere.jpg.