I really love the look of games like Elmgon and Serenity. It is amazing what you can do with pure BASIC without losing much speed now and I kinda wish I could do stuff like this myself. But here comes the problem: figuring out good dual layer ASCII character combination is mega hard. I can't come up with anything good myself, because there are so many combinations to test, not to mention the layers can be offset to create different effects or like in Serenity/Elmgon get rid of spaces between characters.

So what I was wondering, it's if someone or multiple people could post good ASCII character combinations here, or write a program to do so, and describe what the created character could be used for, and if the second layer needs to be offset by 1 or not. Maybe a program could be created containing all chars combinations in 4 strings: two for no offsets (with spaces between each chars on tilemaps) and two for 1 px offset (no spaces).

Excellent idea!  I don't have many good combos yet, but one of my favorites (Serenity style) is E, d.  It's the main sprite in my Elmgon Movement Engine Screenies.