i think it'd be very funny if ultrakill got a secret level thats just a "character customization" screen where all it lets you do is put stickers on V1 and your weapons. and once you have it revealed stickers appear in pretty much every mission in out of the way places you can pick up to use in it
ultrakill: horrors of neverending war, machines fueled off human blood, etc
also ultrakill: decorate your killing machine you play as with cute stickers, also that angel you keep fighting is 100% gay for you