The second title, "Ultrakill Inspired ROGUELITE...?!", is good.
My addition to it would be: Blood Rush: The Ultrakill Inspired ROGUELITE
The thumbnail is awesome. It has all the elements it needs, and positioning is good. Very cohesive.
Assuming character you have there is one distinctly from that game.
If I were to make changes it would be to reduce amount of elements, rather than adding anything new.
I believe Cult of the Lamb is a rougeLIKE, so while it does fit the spot, it would be first to go if anything.
That narrows focus on the two relevant games it is emulating/inspired by.
Do like the effects for the "Roguelite", and the Position of text is good (over and under gun).
The text is fine, but you could replace it with game title, Blood Rush (maybe full caps), with each word replace current position.
It could either maintain that effect you have there, or one could be fully red and the other text white.
The font could remain the same, or maybe utilize the game font/title used for it.
If that is done then drop the "Blood Rush" from title I suggested (to remove redundancy).
Background is fine, maybe colors changed around, but just nitpicking on that.