Peake, best known as the author of the Ghormenghast trilogy, was a writer and artist who had Parkinson’s. According to the Wikipedia article, Ghormenghast was, in part, influenced by his Parkinson’s symptoms.
The images and poems on the charity’s calendar all come from this competition. Apparently there are prizes, too.
The closing date for entries this year has been extended to the 14th of April. I posted mine today.