I have a couple reasons for somethings in this piece
Why a caterpie - It is the worm pokemon why I didn't choose wurple cause caterpie is more Iconic than wurmple and also people who are long time fans/gen onenners (is that how you spell it?) will perfer it (and lets be honest who remembers wurmple)
The brush: One side is a pen representing writing while the other side represents creativity (it's a fake smeargle tail)
The book: reading/writing, I came up with the title and cover design while trying to draw a pie on it (Cater
PIE) and then shroomish popped into my head... somehow