Preferably WW2… but would also enjoy high res even better. 
Here you go:
www1.istockphoto.com/file_thumbview_approve/382537/2/istockphoto_382537_muddy_tracks.jpg
www.digger.ch/images/products/d-2/tracks/Tracks_adaptive_Digger_D-2.jpg
http://history.amedd.army.mil/booksdocs/wwii/actvsurgconvoli/Figures/fig44.jpg
http://milov.nl/files/020607_tank.jpg
www.forceforgood.co.uk/junk/tank4.jpg
www.vac-acc.gc.ca/content/history/secondwar/netherlands/images/pa_42597_neth.jpg
www.army.mod.uk/atra/the_armour_centre/images.htm
http://www.uniteddefense.com/i/prod/ags_mud_Web_100.jpg
http://www.qohmuseum.org.uk/sherman_1.jpg
http://www.25thida.com/TLN/v545_10.jpg
Excellent!
sounds a little nuts but what if you took an old tank model and Lightly rolled it through some mud in your back yard take pics and use it for ref on all later models