I needed some 15mm seated infantry to fill up some trucks and half-tracks and things, so I made some.
British first:
(https://1.bp.blogspot.com/-HgOWcU_6WcQ/YEqKzEAN3UI/AAAAAAAAX50/WjzH1U3hV805SAJj5jZEMOG2Cbk4YKZWgCLcBGAsYHQ/s800/British15mmSeated01.jpg)
These guys are wearing the Mk.II helmet, and mostly armed with the Mk.IV Lee-Enfield. There's also one figure with a Sten, and another with a Thompson.
They're available at https://www.wargaming3d.com/product/british-seated-infantry-15mm/ (https://www.wargaming3d.com/product/british-seated-infantry-15mm/)
(https://1.bp.blogspot.com/-czJGcVwlZho/YEk5BiLKaiI/AAAAAAAAX20/X4yF_VecPnUIxtqzXxCnd_mAL1xcl77LQCLcBGAsYHQ/s16000/2021-03-11-3dPrintedSeatedBrits-001.jpg)
These ones are wearing the Mk.III helmet, that came into use for the D-Day landings.
This set can be found at https://www.wargaming3d.com/product/british-seated-infantry-15mm-mk-iii-helmets/ (https://www.wargaming3d.com/product/british-seated-infantry-15mm-mk-iii-helmets/)
And also some Germans. These are early WWII infantry, wearing jackboots and without helmet covers.
(https://1.bp.blogspot.com/-Vh2zq6GcAKU/YEqJi5AvT2I/AAAAAAAAX5c/Ddf6Hz7482Exs5Auv6G1kXwNllIe5lzQwCLcBGAsYHQ/s800/15mmGermanInfantryEarlySeated.jpg)
They can be had at https://www.wargaming3d.com/product/german-infantry-15mm-seated/ (https://www.wargaming3d.com/product/german-infantry-15mm-seated/)
I've found that best, most natural results are to be had by combining the figure STLs with that of their transport, and printing the whole lot as one, as I did here with this 15mm SdKfz 7.
(https://1.bp.blogspot.com/-xGBcT4RooMc/YEqJxPQuHnI/AAAAAAAAX5k/Ps_ilqvWNekBw2v9_gv6Up2DyftuAs46QCLcBGAsYHQ/s800/15mmGermanInfantryEarlySeated_SdKfz7_02.jpg)