Hi! I have struggled before with creativity issues, and I have a couple quick fixes for it.
1: listen to music while you're drawing or observing the model. It can make your drawing come out with more flow or with a different colour scheme than if you didn't have music.
2: try drawing without a sketch. Start from the inside and don't worry if it doesn't come out perfectly, because it won't. And that's the beauty of it.
3: explore the opposites. Instead of painting a green tree, why not try and paint a pink one? It gets more and more interesting as you change the colours.
These were my top 3. If you need more feel free to ask!
