Sarcasm is fun until nobody can tell when you mean anything.

Sarcasm works by contrast with how you normally talk. Use it constantly and the contrast disappears, so people lose the ability to tell your real approval from the joke version and start discounting the compliments along with everything else. The cost turns up later, when you want to say something sincere and nobody can hear it.

Say one plain, unprotected thing a day: that you liked the drawing, that you are glad they came. No tone, no safety net. It feels exposed for about a week and then it hands you back a register you can actually use.