The above two artworks were conceptual character designs for an unmade animated version of J. R. R. Tolkien's Hobbit, a few more can be found at the bottom of this article on Trnka. Arabian Nights artworks found at Michael Sporn Animation. See more of Trnka's artwork at 50 Watts.
Equally impressive to Trnka's artwork is his animation, below is an assortment of his beautiful stop motion animated works.
"Dva mrazíci" Jiří Trnka (1954) from Mecca_Audio on Vimeo.
The hand - (1965) - (Jiri Trnka) from Roberto Pernas on Vimeo.
Jiri Trnka - Kyberneticka babicka (1962) from Jakub Ptacnik on Vimeo.