BYTE had some great cover illustrations too, and IIRC, even some of the articles had great diagrams or drawings. IIRC there was an artist called (Robert?) Tinney who did many of the best looking and most famous covers, including maybe for the Smalltalk issue - which I think had a multicolored balloon on the cover - just searched and this is it:
https://cdn-images-1.medium.com/max/597/1*9qr-I3aJLr0IrM256g...