If you are going to shade, I'd suggest using much darker shades though. Many of your shaded vehicles incorporate very pale shading and along with dithering mean there is very little visual effect and the shading is almost invisible on many of them. You should try and avoid having a straight band of shading on the bottom. The sun would have to be perfectly above for that, and in that instance the side would still be darker shaded because of the lighting angle in that case.
It is hard to explain shading unfortunately...
Here is one example to look at anyway. These ones are a bit like yours, note how dark the shading is compared to the base colour, and how on the larger boats and vehicles the shaded is "curved" rather than straight across: http://www.spriters-resource.com/ds/scri...eet/27414/
I don't expect you to copy the style on that sheet but it should give you an idea of what you could do. You at least want to make sure the base colour of the vehicle and the shading is quite clearly separate though.
It is hard to explain shading unfortunately...
Here is one example to look at anyway. These ones are a bit like yours, note how dark the shading is compared to the base colour, and how on the larger boats and vehicles the shaded is "curved" rather than straight across: http://www.spriters-resource.com/ds/scri...eet/27414/
I don't expect you to copy the style on that sheet but it should give you an idea of what you could do. You at least want to make sure the base colour of the vehicle and the shading is quite clearly separate though.