Image repository web for 3rd people image uploads

I am searching for a website where I can upload images in a folder of the repository, and other people (people unknown) can upload images in the same folder, without deleting the existing files.

I thought about GitHub but is quite complex maybe for new people. I tried Google Drive, but it does not work as I want: if I give permission to 3rth people to edit, I can not protect the current files to be eliminated.

Does anybody have a suggestion about it?

[Rik]

How exactly does this relate to Matlab?

Feel free to reopen the question to edit it to make that clear.