Render in Blender with RGBA (rather than RGB), with Quadratic anti-aliasing at 11 ("full sample" seems to make no difference that I can detect), then place the images produced thus by Blender straight in the relevant /images directory, and refer to them in the .dat files. For road vehicles, which is what I am doing at present, I use the "normal" rather than the "vehicle" 8 view rendering, and apply offsets. An example of the file names and offsets are as follows (note that this includes livery definitions which are unique to Experimental; they can be removed by deleting zero in square brackets before the = sign.
EmptyImage[E][0]=./images/aec-rml-trolley_E.0.0,-33,14
EmptyImage[SE][0]=./images/aec-rml-trolley_SE.0.0,-13,0
EmptyImage[S][0]=./images/aec-rml-trolley_S.0.0,4,0
EmptyImage[SW][0]=./images/aec-rml-trolley_SW.0.0,-8,10
EmptyImage[W][0]=./images/aec-rml-trolley_W.0.0,4,5
EmptyImage[NW][0]=./images/aec-rml-trolley_NW.0.0,12,10
EmptyImage[N][0]=./images/aec-rml-trolley_N.0.0,0,33
EmptyImage[NE][0]=./images/aec-rml-trolley_NE.0.0,0,24
For rail and other types of vehicles, use the "vehicle" setting in the script and apply no offsets.