I think a boho reading corner is a great idea…wish I had enough room in my bedroom for that!
I am in no way an expert on matching patterns and stuff, and I don`t know a lot about what stores are good seeing as I live in Norway, but these are some of the things I think of when I buy cushions
The great thing about boho is that it doesnt really have to match... to some extent so you cant go too wrong. If you have a colour palette a tip is to find colours that go together, or that look good in your room. Maybe find some cushions with patterns with at least one colour that is the same. Kate always says things look good in threes, though that is more important in a whole room, not just cushions. For instance, none of my cushions are really the same exept some of the patterns contain white. Maybe some cushions that are more neutral.I have also found that different textures can be just as important as mixing patterns, it adds a lot to the space.
TIP: I always buy cushion covers as they take up way less space when I want to change my cushions (and they are usually cheaper!!)
But the most important thing is that you like how it looks. There are not really any rules to this. See what you think looks good together