They're a bit messy. The basic outlines seem to be correct but I just can't understand the logic behind your shading. Looking at the green tank, I can tell it's a tank, but there isn't really anything to give it volume, it's just a tank-shaped blob. Here's a quick edit of it to show you how I'd change that:
(Not based on an actual Sherman, just a generic tank here.)
The main thing I'd pay attention to is defining the edge between the top and the sides, then maybe you can add a couple tiny details to make it more interesting.
The tiger colors are a bit lacking in contrast and I'm not sure why you drew the tracks with a smattering of random pixels like that.
Tiny stuff like this can be really really hard, it usually take a lot of tweaking to get something that looks good.
