Hi Mark,
I see you are obviouisly a fan of this British workhorse judging by your user picture!
The 6pdr is a nice weapon to model, unfortunately the Tamiya kit is an old dog that doesn't do it justice, I won't even get started on the kits flaws!
However, it looks like you've done a good job of painting this kit up, and I see you went for the seared mud camouflage on the shield, this is a nice touch but perhaps a bit heavy. Also as Jim says if you are going to add mud to the gun trails it should be on the tires too which are desert versions not ETO, (whoops I've started!

).
The figures look good, but the helmets shouldn't be the same kahki as the uniform, more like the green of the gun.
Also perhaps try mxing your paints to get slightly different uniform shades, as individual garments would all be slightly different colours depending on their age and batch in which they were made. Can't tell from the pics if you've applied any washes or drybrushing to them, but this often brings out the fabric of uniforms well.
Please don't take this as critisism, im just trying to give you some hepful pointers.
If you fancy giving the 6pdr another blast at any point, Zevezda/Italeri did a kit a while back that, while not perfect, is a LOT better than the Tamiya version. I recently built and updated one that is awaiting paint at the minute. I think its OOP now but you can still find them if you shop about. Resicast do some lovely resin versions too, and an ammo set which is nice.
Good work, keep it up, its always nice to see British armour being modelled!
James