Hullo Ozzy, dont get discouraged so fast, lots of views and few replies generally just means people dont know what advice to offer. In some cases, this is a good thing, and means your work is solid and noone can think of a way to improve it, in other cases it means its outside of everyone who has looked at its comfort zone, or there are a lot of lurkers.
In this case, I think its a combination of all the above, and your primary problem is posting a large amount of unrelated images. Focus on one piece you want critique on, and you will probably get further.
So, that being said.... I love the turtle. I think the gray shadows hurt it a little bit tho, and it could benefit from more saturation on them, The bird appears to be pillow shaded, and that just erks me, the little man... confuses me stylistically. He has a top lit hat, and a side lit body, first off, and appears to be proportioned in a way that only makes sense if he's flat, yet the shading style suggests he is perfectly round. The frog in the hat is awesome, as far as line work goes, but I think the dithering really hurts the piece, especially because it is inconsistent. Either extend it to the hat, and use some on the chin (do frogs have chins? The area under the lips... do frogs have lips?) or lose it altogether and add a new shadow color.
Now, that being said, none of that critique was full or focused, and I basically just glossed over the biggest 'at a glance' issues I could come up with, yet my post is already pretty long. Focus on ONE thing you need/want help with.