I just gonna say that design 2 is hard to read. The letters are on the deep area enough, so adding more black on a dark background would never work.
Design 4 is okay enough but with solid color letters and solid colors border without anything else, it looks boring.
Design 3 is pretty nice. It's readable and the little gradient of the letter give it a nice touch, but if i were to say which one would i like, i would say design 1. The color gradient of the letter is very nice, i like the color, though it somehow looks a little grayish, but it was just my opinion.
{Design 3 was placed in after design 2 in my device so it got me confused for a second when reading the reply lol)
And maybe just an addition you didn't need, but the elf looks super dark and unless i make my brightness up, his(?) Face is hard to see. Maybe put some light there?
Anyway, this is super long but just gonna say that the cover looks great.