@demetri79 The way that a texture is mapped to a model is not decided by Isadora, it is set when the UV mapping for the model is made. This lets you specifically set which part of an image goes to which part of a models surfaces.
To do this with a cube will not be so difficult - take a look at this explanation: https://all3dp.com/2/blender-u...
There are a lot of Blender tutorials online covering this.
You can see here though that each side of the model gets its texture from a different part of the image that is being used to texture it. You can render a video that has all the smaller videos in place so they match the texture map and then play that in Isadora and feed it into the texture input of the 3d model player.
You can also dynamically create this - you can have 6 different image sources and then combine them so they have the same layout as what the model expects for its texture and UV map. You can use a virtual stage to do this. With each 6 image sources, send them to the same virtual stage and on each use the mapper to get the source content and place it on the precisely correct position and size on the virtual stage. The size of the virtual stage should be set to whatever texture aspect ratio was used in the model, ie if it was made with a 512 * 512 texture then make a square texture (you can use the texture scaling to correct things if you need).
Then when all the 6 pieces are being sent to the right locations on the virtual stage, you can get the image from the virtual stage and send that to the texture input of the model player. This will let you send any video or image to any side of the cube and be able to control the content for any side independently in real time.