Having trouble coming up with something to draw? No worries - while you'll eventually learn how to start from a tiny seed of a thought and gradually nurture it into a complex concept to explore through design and illustration, it's perfectly fine not to be there just yet.
For now though, here's an idea that might interest you.
D&D Creature Redesign
Dungeons and Dragons is full of all kinds of interesting creatures and critters - take a species and redesign it, using a real-world animal as its basis. Looking up the creature you're redesigning certainly helps, but try not to dig too deep into existing drawings of it. Textual descriptions are often better, as you're not going to end up polluting your mind with other peoples' interpretations. Even better, consider the origins of those creatures, as Dungeons and Dragons generally picks bits and pieces from other source material - from which you are welcome to pick and choose as well.
Take this kobold for example!
It's designed after a pangolin. Kobolds were originally house spirits from germanic folklore, but can go as far back as the Kobolds of greek mythology. They can range from helpful, doing chores and helping around the house, to being mischievous and ill mannered. These pangolins, as explained here perform a very specific task - making maps - and are quite mischievous in their desire to share them with others.
So - pick any D&D creature, do some research into its origins, and try to take it in a different direction.