first off this is extremely cute and very well drawn. the use of lines to show Gugrurumon's speed is lovely and the simplicity of the background draws your attention to Gugrurumon even more. i also like how you've left footprints in the snow behind. my main critiques are the tree in the background, perhaps they could be a little more like silhouettes than thin lines. your scanner also seems to have left lines across the picture, and maybe you should crop the edges where the edges of the paper are visible. overall i think this piece is very effective and would very nice if it was transferred to digital and coloured.
The fact the character looks more cheerful gives a great positive feeling, the design has a retro look but yet it is modern at the sametime, the fact that it looks unique makes it even more interesting and who couldn't love a jolly creature that is happy outside, in the nice weather?