The current Microsoft Remote Desktop icon appears to only contain 256x256@2x, 128x128, 32x32@2x, 16x16 image sizes.
Apple's recommendation for ICNS is:
512x512 pt (512x512 px @1x, 1024x1024 px @2x)
256x256 pt (256x256 px @1x, 512x512 px @2x)
128x128 pt (128x128 px @1x, 256x256 px @2x)
32x32 pt (32x32 px @1x, 64x64 px @2x)
16x16 pt (16x16 px @1x, 32x32 px @2x)
Right now the icon looks grainy in certain scenarios.
Adding these sizes to the ICNS would improve the look.