Don't like the My Block Icons available in EV3 to identify a my block you create? Make your own My Block Icon or edit an existing one.
My Block Icons are stored in "C:\Program Files (x86)\LEGO Software\LEGO MINDSTORMS Edu EV3\Resources\MyBlocks\images".
Look in the folder and find the PolyGroup... .PNG files. They are numbered 000 to 097 and there are 3 associated PNG image files for each number; a Diagram, a Pallet and a Pallet_MouseOver for each one. You will notice that many numbers are missing. Now open the EV3 software, start a new program throw a program instruction on the start icon, select it and go to Tools - My Block Builder. When the My Block Builder opens you see the screen where you can select an Icon for your MyBlock. You will notice 10 empty Icon locations on the bottom row. In the Images folder I copied 070 to 079 (10 numbers, 30 files - the 76 is a duplicate of 076 - do not copy) to a New Folder, renamed them 080 to 089, and edited them with MS Paint (a smiley face and numbers 1 through 9). Then copied them back to the Image folder. Opened the My Block Builder and used the new My Block Icons in a program to test. I'll let the kids edit them with MS Paint to make them look however they want. The Builder PNG image files need to be 34x34 pixels, the two pallet files need to be 25x25 pixels.
The Image Folder.jpg shows some of the PNG files I added and how I renamed them 080_MyBlock, 081_MyBlock_1 etc..
The My Block Builder.jpg shows where the new My Block Icons (080 to 089) were added to the menu of Icons