Probably I am doing something wrong and hopefully a simple fix - I am seeing the up triangle sprite overlaid on all sprite images when using a custom theme. As seen here.
I had gone through the process of creating a custom theme based off of material through here. In the generated kendo.custom.css file, I replaced all references to images (url('none/sprite.png'); with the proper path on my web server.
Everything looks fine with standard material theme:
But the sprites become overlaid after I specify my custom theme: