Serial numbers do seem to be relatively uncommon on US Army M10s and M36s. They were more common on the M36 than the M10, from what I can see. The serial number was normally positioned on the hull side near the front.
You probably don't need 4 of the tank destroyer battalion insignia (i.e. the black panther head) - 2 will do.
You've actually got two different (incomplete) sets of French unit markings there - the 'Cross of Lorraine' appeared vehicles of the Regiment blindes de Fusiliers Marins (all former French Navy personnel), while the 5th Armoured Division used the big white diamond on French colours. French vehicles had their own fancy serial number as well, painted in white on a black rectangle with the French flag on the left side. This appeared on the front and rear.
Nice to see you've included the British registration numbers (with the 's' prefix, signifying a self-propelled gun). The '51' in a red square wouldn't appear on a British M10 or Achilles - they were crewed by the Royal Artillery, which used a red over blue square (like the one with a '77' on it that you've provided, which is correct).
These vehicles were widely used by the anti-tank regiments of the British infantry divisions as well, so maybe include a few infantry division formation signs? For the infantry, the regimental sign was also a red over blue square, but with a '46' inside. The RA had very complicated additional markings, so maybe don't try and cover all of them.
If you need some space, you could ditch the stars with yellow circles (as they were only used for a short time) and the US armoured division patch (since, as previously discussed, this almost never appeared on vehicles)...
