EnderGamingFilms

This is indeed a dupe of what I posted on the art page b/c I did not know where exactly to post my problem... So I have some are for my modpack what is the file size for the picture or do they have to actually be the size that it says or cna i just compress my art to make it a smaller file size b/c rn it is 3 mb and it still gives me "413 Request Entity Too Large"... What do I do? Also my art is Ultra HD (3840x2160)