Sorry, but I do not understand which the problem is. My original pixel art is at 512x1512 pixels (the big image) then I created the preview rescaling it to 100x100 as it needed to be. This can't be done? What do you mean by re-size rendering?
Thanks in advance.
Your preview image has a re-size rendering, which is not allowed. It can be replaced by clicking the edit button and changing the preview file.
Also, it's encouraged to submit pieces at x1 as PJ has a zoom function.
By the way, I don't know why 2 of the same pixel art works about death were uploaded accidentally. Could you delete 1?