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.
Hamelin at War
The Pied Piper has failed. He came to the stricken town of Hamelin, and promised to be their salvation. You see, the town has been suffering from an infestation - a veritable plague - of rats. They're everywhere, in everything, nothing goes untouched by their little grasping paws.
The Piper's promise gave the villagers hope, but it was not long lived. His bewitching tune drew the beasts out, brought them streaming from the houses and from the shops, a tide of fur and filth and- oh, the stench of it. I believe it was that, the smell, that caused him to flinch as he played, and the sweet tones stopped suddenly in a cacophony of choking gags.
It was a brief stumble, but that was all they needed. Their eyes snapped open with awareness, and the horde flung itself at the poor Piper. In seconds, he was gone.
Now, the rats are no longer hiding. Hamelin is at war.
Pick a side - either the desperate townsfolk of Hamelin, or the conquering rats, and choose some aspect of their struggle to design. A hero character, a weapon made purposely for exterminating rats (or to be used by rats!), or even consider the physical defenses the villagers would use to keep the creatures at bay.