It really depends on the condition of the trench.
Most trenches were under a lot of artillery fire and would end up looking that rubble like in the photo. A newly built trench could look pretty uniform/decent like the trenches in the game.
It also depends on who built the trench. For example the french trenches were know to be very primitive up untill the end of the war. Then on the other hand you had the german trenches which were the best built and most complex trenches in WW1. That's why the allies had so much trouble breaking through german defenses on the western front because the german trenches were very heavily defended and extraordinary well built.