I don't know what to do with the background

[hearty steppe]

the dark background and the counter already give the information that they are at a bar. you could keep it as is imo.

You could maybe try to add some dim lights to establish the atmosphere?

might be inspirational for the lighting ?

but in general i recommend planning the background in the sketching phase. Its harder to do so around already fully illustrated characters

[keen hamlet]

this is so cute-!?

[marsh sable]

tysm for the advice, i do do this usually but the drawing was just ment to be a doodle and i got carried away 😅