Thanks for all the comments guys, that's some proper constructive feedback there. I'll attempt to reply to all of the points you've mentioned:
a)
The ear - yeah, I know, it's rather simplified, the way I draw ears. I guess it's something that I grew doing through my comics (
example, see rest in signature link). I might revise that, it wouldn't be much of a bother to change it.
b)
The arms - to start with, I'm still learning to pay attention to proportions in general. I thought that here, I got the length of the arms right (well, compared to my usual standards). Changing the jacket's crease on the right arm is a good idea, I'll change that too.
(The hands don't have creases, nor fingernails, because those are supposed to be gloves - there is proof for that in the text. Might improve that area later.)
c)
The horse's jaw - what can I say, first time I draw a horse.
d)
The head - again, it's the style that evolved through my comics. It seems that every time I draw a face, it somehow fills up the whole length of the head.
e)
Shading - I might as well do that too when I get to addressing all the previous problems.
Being honest, I was eager to post this before the weekend, since I've just returned from travelling. That's probably why the picture looks the way it looks. Again, thanks for pointing out these faults, much appreciated.