Thank you so much for a detailed response @JohnGrayson !
We are really glad you were able to send us an example of the clip raster function.
To answer your question and give this a bit more clarity, we would do have control of the image services but we would not have control over the polygon layer. The image services will be added to the map all formatted in the same manner as NLCDLandCover2001 ensuring the same raster attribute table is used.
It is neccessary that we would want the polygon layer to come from a shapefile only.
The desired used experience would be that they would upload a shapefile boundary of their choice and in turn this would generate multiple landcover charts for all the image services that have been added to the map ( Which is why we ensure that the image services would use the same formats). Something like this multiple charts image which uses the same sample for two different raster layersMultiple Charts image
The charts would be the desired output. We do no need the clipped raster layers to be added to the map but if we have to its absolutly fine.
Please do let us knwo if you have any insight on this.
Thank you again for all your help.