all the monsters could use some more contrast
and all the sketches look happier, more playful, i think you should try to get that in the sprites. thinks like the short legs and beady eyes on the human
i prefer the top right style of shading and outlining, gives the most pop in the depth, plus not everything is outlined
i think you should shade the human a bit more though, like under the arm, and the arm itself, maybe the crotch too
the rock doesnt appeal to me at all. seems like a blob with some parts sticking out, i suggest you restart on that one and make it a bit bigger as well
the fish has the best shading of them all i think. clear shapes, not too much or too little of each colour, nice balance
maybe add a bit of shade on the middle of the assfin, where there now is a highlight
put a bit of a line on the lower part of the eyes and work on the lips a bit maybe
allso add some more decal like the stuff on his head.
lastly he lacks toes
the furry is nice too, but he needs some eyesockets and better fur. have you tried using a bit larger spikes of hair? more trianglish and dont just mirror the shading, lazy bum =P