PxrRandomTextureManifold with PxrMultiTexture to assign random textures to many objects:
PxrRandomTextureManifold can only be used with PxrMultiTexture.
The number of texture you want to use. You should have at least one texture and PxrMultiTexture supports up to 10 textures.
The order in which PxrMultiTexture will assign its textures to the objects.
Textures ordered based on the random source. The number will wrap in the 0->numTextures range.
When using the textureID PrimVar, the texture index will match the primvar.
|1||Random||Textures randomised based on the random source.|
For each object to get a different variation, you need to select something unique about them to create a unique seed. You have a choice between the object's id, the object's name and a "textureID" primitive variable.
Attribute "identifier" "float id"
Attribute "identifier" "string name"
"constant float textureID" 
If you want one of these patterns to compute a different variation, set the randomExtraSeed to a non-zero value. This parameter will only influence the randomization parameters (randomOrientation, randomFlipS, etc).
Randomize the orientation of the textures by randomly swapping s and t.
Randomly flip the direction of s.
Randomly flip the direction of t.
Randomly offset s. You should probably avoid this if your textures are not tiling seamlessly.
Randomly offset t. You should probably avoid this if your textures are not tiling seamlessly.
Global rotation angle around the origin of the st domain.
Scale the st domain while preserving the aspect ratio defined by scaleS and scaleT.
Frequency of the feature in S.
Frequency of the feature in T
Offset from origin in S.
Offset from origin in T.
Invert the direction of T.
Name of custom 1D S or 2D ST primvar.
Name of custom 1D T primvar.
Select the objects you want to add the primvar to and run the MEL below.
addAttr -at "float" -ln "rmanFtextureID" -k true -dv 0.0 `ls -sl -dag -shapes`;
rmanFtextureID will appear in the channel box and the attribute editor so you can set its value and will be exported by RFM as the expected
float textureID primvar.