asked for help with watercolour backgrounds.
This wound up mostly being about drawing. WHOOPS.
I should also mention, the most important part of all:
REFERENCES. REFERENCES. THEY'RE YOUR NEW BEST FRIEND.
Seriously, look at a few hundred or so pictures of what you want to draw, do studies of them to get the feel down. Incorporate elements from different ones. If you're doing a specific sort of architecture (or whatever else you want to do specifically), research the topic and learn the terminology so you have a more thorough understanding of what you're looking at and how to change it. You can do whatever you want with your keystones and flying buttresses if you know what the hell they are and what they do.
Feel the reference. Be the reference.
This tutorial, being slapdash at best, was mostly done loosely based off of this image
Because I'm absolutely loopey and I have researched into it, without looking at the information in the picture I know it's a 17th century french room. I know the people of the era wore powdered wigs to try and prevent head lice. I can deduce that because women wore such huge dresses at the time, those chairs were probably not built to accommodate women. Et cetera.
(also note that your painting never has to look exactly like the picture you're working from. Just focus on making your painting look good on its own rather than like the picture.)
Other tutorials from me: