Well, I'm not a background expert, but what if you used a brush as thick as for the characters, but slightly paler colors? owo

I like the backgrounds you made for me more or less

Well sometimes in the inking process the picture is mostly done beforehand. That is to say the line work is completed and then the inkwork is added on top of it. Use a separate layer for the background sketch, line it first without inking it yet to better understand how it looks normally, and then add ink accordingly to see where and how it fits, if it does. Painted backgrounds can be nice as well but can sometimes take long amounts of time to add detail and make it more vibrant in terms of lighting and shading and not looking like a blurred mess.

Vrghr is no artist, but one trick this wuffy has seen others use on various streams, is to grab a suitable photo for the subject and drip it into a separate layer. Then use various "warp" tools to bend and twist it to fit the perspective and size. Finally, apply another layer over the photo, and use that to sketch out different objects and elements from the photo. You don't want the entire photo (unless it is public domain). But using the elements as reference to bring in buildings, fences, trees, etc., can help you speed the background process.

Then just fade the photo, and complete your background coloring, linework, etc., as normal.

First of all, happy holidays. :)

Secondly, I'm no expert in backgrounds since I often find backgrounds to be a major pain in the arse quite frankly. I often focus most of my work on the character(s) first, lol. You on the other hand are better than me on backgrounds.

NOW with that said, have you ever considered colour holds? I haven't experimented with this yet myself. However, on paper, this could be the solution. By "colour holds", I mean you have a few layers for linework, or at least one layer per character's linework, and one layer for the background layer's line work. Then you alpha lock each layer and colour the linework to be darker than the colour it surrounds. For instance, use dark blue lines around light blue, or an extremely warm dark grey (to the point of almost being black) for dark red, etc. The main character's/characters' outline can be black if you wish, but colouring the linework of the backgrounds could be a viable solution. Or if you choose, you can colour all the linework, but make the character's/characters' linework much darker than the background's lineart.