Illustration is tough. It mostly isn’t about what you want to create, it’s more about what you can create for your client. Most of the stuff we hire watercolor artists for are historical maps for things like battlefields or city history. You’d get a bunch of research material and some direction, do some sketches, then a rough semi-fill of color. Once the direction is right, you finish it. Under deadline and on budget.
If you can hand-letter, even better. Then we don’t have to hire a calligraphist.
Some of the other things we’ve had illustrated in color are native flora and fauna for specific areas maybe for a zoo or nature park, and again, historical battle scenes for which there are no photos (like the Revolutionary War, etc.) Clients are getting sick of seeing the same old historical photos used for the Civil War too, so there is a bit of work there.
We’re not into advertising, but there could be something there for you as well.
Most times we work with an agency or artist representative (though I just found out the two sites we normally use are shut down, so that doesn’t bode well.) Here is one where you can check portfolios to see what they do.
Illustrators are hired on style. So have a style and stick with it. While your art is very good, it doesn’t stand out. At least not for what we do. But there’s stuff in that portfolio link that I couldn’t imagine ever wanting to use either.
But it’s not about me.
It’s all about the client.