I don't think i catch your drift about the behind the cage? You want a seperate render of the cage.... without door? and a lose render of the door to put in front of the girl? renpy can do that easily...
The ogre in the left cage is inside the cage... in animation i wanted to have it put it second hand on the bars... and make the cage shake a bit. maybe 5-6 frames. 1 orginal, 1 to add the hand, maybe move the left leg for rocking, then tilt cage left a bit, 1 tilt left more... return to tilt left a bit, return to 2 hands on cage.. tilt to right a bit... tilt to right more... tilt to right a bit... to hands on cage... 1 hand on cage... loop.
The dog i just want to move a bit about.. because it isn't really visible...so changing shadows and stuff.
It will take a while to render.. because unbiased (reallife like) renders need everything in the scene to get the same shadows.