@xenevra, just to be safe we have to make sure that any images added by suggestion are free of copyright and/or are appropriately attributed. In order to include the image we have to make sure it’s from an appropriate source and that the source is cited beneath the image itself in order to be able to safely include it in the deck.
It’s also worth noting that you are free to make as many local changes and edits to your cards as you want (I often do this, because I also like to include images to help make something memorable). However, to include them in the deck as edits for all users we do have to abide by copyright rules and the like. 