Good job practicing your foundations like anatomy and perspective. Once in a while try scribbling quick gestures. like 1 to 2 minute gestures it will definitely loosen up your drawings. Play around with line weight.
Just draw your ass off. Whatever you do, don't -- stop -- drawing...
I like your style, though I can see where Maerrick is coming from with his tips for loosening it up a bit. To be honest, I think I'll follow up his tip myself, for that matter.
The image that immedately caught my eye was the Monkey, nice expressive sketch. It looks like great material for a stylized (vectored?) logo. At second glance I was also impressed with your drawing of the in-train perspective. you should get bored there more often.
I would say, your weakest sketch would be the first image in post #3. Study the anatomy of the animal more, and don't 'give up' like you seem to have done with his head.
On a side note, are you Dutch-speaking Belgian by any chance? I'm Dutch myself, and haven't seen many Dutch/Belgians around the forums.
Finnally im back at home after 2 weeks and so Ive got to scan some new pages
I hope you'll like it
1. 2 of the many model sketches the had us make with sketchmarkers
2 & 3. We went a day to the zoo, where weve drawn animals for inspiration for the robot assignment (posting some of that later on this week)
4. other drawning from boredom