[Moseby]

So the best would be if I could take like a Facebook group and just "paste" it in some code so it takes all pictures from that facebook group ever posted and make them as background picture,

That could probably not work,

I want something that I could collect a bunch of pictures, and they would stack up as tiny boxes.

Like squares all stacked next to each other,

Possible?

[Exemplification]

Graph is fairly simple so requesting photos from a group is pretty simple. Refer to this post on StackOverflow http://stackoverflow.com/questions/48695...e-graphapi

As for displaying them like a mosaic, you're in for a performance hell. Loading many photos is going to significantly impact your page load times. That said you can refer to this fiddle that displays how to make a mosaic of photos. http://jsfiddle.net/webtiki/zMMH5/

It doesn't mean that there isn't one, but I do not know of a solution already made that fits your desires so you'll probably have to hack your own solution together.