I did it.
Did you credit the creators behind every piece of art in your game?
Also, from a legal perspective, you'd be hard pressed arguing that what this game does is fair use. First, it's not really transformative; you're not using the art to create something markedly different from the original - if putting the art into an order and adding some unrelated text was fair use then I could legally just take peoples art, shuffle it around, put it into a photo album, add some story captions beneath it, and then host it on my website for personal exposure and ad revenue. Second, you're using the whole artwork without altering it or adding to it meaningfully. Third, if it came from a paid site then you using the work would be considered to be reducing the value of the artists product and affecting his ability to profit from it - even if you are not profiting yourself.
Some clarifications for above commenters:
- Putting characters in a different context but creating your own artwork is fair use. This is not comparable. This is taking the art itself.
- Using pieces of artwork in things like collage paintings, or as samples in markedly different pieces of music is also fair use in most cases. Again, this isn't that, it isn't being added as a layer of a more complex song, or a small part of a new picture in a new artstyle, it's just someone taking the picture, using it in the exact same purpose as it was intended, but putting some text around it.
- This piece gives access to the original image file to people who can unpack the game. It would be unedited and it came from a paid site. That's very much not fair use.
So yeah, if you're doing it without the authors consent then it's almost certainly illegal. It's also pretty immoral given you are using other people's work to make yourself look good with little likely benefit to the original authors, which is different to the pirated games hosted here which make their creators look good and can lead to people buying things from those creatives.
Whether or not that is appropriate for this site is, of course, a separate question, one which I have no desire to litigate.
(All of this is using US law as a guide, and given they have the broadest and most lenient interpretation of fair use in the western world, it would be more illegal elsewhere)