Yeah, you can use whatever engine and tools you like.
When it comes to the user being able to change resolution that's fine too. But your game should by default open at 64x64 (or lower). This is the resolution most people will play at in the jam context, so opening up in a higher rez will cost you in the ratings. For something like default splash screens that are higher than 64x64 and can't be avoided, most people will understand this and not hold it against you as long as the game itself adheres to rez restrictions.
I hope this helps answer your question!