I found these cool designs here. They mix a good sense of humour with some Torah.
or this for Rosh Hashanna (representing the sounds of the Shofar!)
This one is a little subversive: [The phrase from Pirkei Avot, "Be moderate in judgment" alongside the 4 categories of death-penalty according to Halakha.]
And in preparation for Yom Kippur - for those with a gory sense of humour - here is the "Avoda" T-shirt:
FRONT and BACK
Hat tip - Ynet