The nature of the fights and the opponents were very different.
In the European Theatre of Operations, allied tanks crews often fought for long periods of time across very long distances. As they traveled, they tended to accumulate/liberate all manner of stuff and take it with them. The opponent usually fought delaying actions--hit and run--and tried very hard to preserve men in the process. Tanks were regularly knocked out, yes, but crews often survived and their equipment was quickly recovered.
In the Pacific Theatre of Operations battles were often relatively short, punctuated events. For example, the battle for Tarawa lasted three days. Then it was off to prepare for the next mission on another island. Crews simply did not have time to accumulate as much stuff. The battles often took place in less built up terrain so there were not as many civilian items to liberate. The enemy placed very little value on the lives of individual soldiers, regularly launching massed infantry attacks and fighting to the last man. Anything on the outside of the tank could very well end up in the hands of the enemy and used against the crew. Further, tanks often had to hose one another off, making the outside of the tank a very bad place to store valuable possessions. Allied tank stowage in the Pacific did evolve over time, but mostly to increase the defenses of the tank. This probably reached a pinnacle on Iwo Jima with the 4th and 5th Marine Tank Battalions. Based on reading and pictures, defensive and stowage arrangements were usually decided at the battalion or company level before each mission. After a mission, equipment was recycled and prepared for the next.
For Okinawa, the US committed 8 Army and 2 Marine tank battalions plus 2 independent Marine tank companies totaling over 800 tanks. The stowage varied widely by unit and tank. Further, the battle was long enough that stowage and defensive measures evolved during the fight. Even some of the Army tanks received extensive defensive upgrades like wood planking, concrete, and track link armor.
The
Hard Corps Models website has some pictures of tanks used on Okinawa in the reference section.
Tank Battles of the Pacific War by Zaloga has a section dedicated to Okinawa.
Good luck with your project!
-Doug