As for German stuff, yes the Pz IV late variants were quite common in the Ardennes, along with Hetzers, StuGs, Panthers, Panzerjager IV variants.
On the US size, there were many common vehicles - Shermans, such as the M4, M4 105mm Howitzer, M4A1, M4A1 76mm Wet Stowage, M4A3 75mm Wet Stowage, M4A3 76mm Wet Stowage, M4A3 105mm Howitzer, M4A3E2 "Jumbo" assault tank, and a few M4A3E8 (with more arriving in 1945). The light tanks were M5A1s with a few early M24s coming for the Bulge battle and some more arriving for the counterattacks in 1945. The armored cars were still M8s, with some M20s (mostly in TD units). SP artillery was based on the M7 and M7B1 "Priest", the M8 Howitzer Motor Carriage, and a few M12s. AT guns were 57mm, with some 3" guns in towed TD units. TDs were M18, M10, M36. Lots of halftracks including M2A1, M3A1, plus mortar carriers, and AAA vehicles - M16, M16B, and M15A1. Towed artillery included 75mm Pack Howitzer, 105mm M2-series, 105mm M3 (infantry cannon companies and airborne units), 4.5", 155 howitzer, 155 gun, 8" howitzer, as well as the big 8" gun and 240mm howitzer and 4.2" Chemical Mortar.
Lots of opportunities for new stuff out there!
Gary