Cool creature concept! Wanted to address your concerns about the lighting and three quarter view especially. I pulled a couple of references off of google for a bird at three quarters view and antlers so I could get a feel for how the features should sit in space. Since the tail is going to be pointing towards the back of the scene in a three fourths view, some of it is going to be obscured by the body. Just a little bit of the tail showing is enough to indicate its shape and position while reinforcing the idea that the titmouse is angled towards the viewer. For this iteration, I actually ran with lighting from the top left since this is a creature concept and most of the visible body is to the left. Lighting from the top right is also perfectly fine, it just means that for this drawing most of the creature is going to be in shadow, making for a more dramatic or moody scene. You have some really nice saturated shadow on the antlers, which I tried to preserve in the paintover. Depending on your drawing program, it's generally a good idea to do the shadows on a separate layer set to multiply for cell shading. It makes it a lot easier to go back and make changes if you want to try out different lighting angles. Big thing with shading is to visualize complex objects as a series of simple shapes, spheres, cubes, etc. If you can cell shade the simple objects, you can start generalizing that out to the more complex objects. Here, I see the antlers as warped planes with some thickness and some attached cylindrical points, the head as a sphere, the body as a more squashed sphere, and the feet/claws as a series of connected cylinders.