Hey folks,

This is not really worthy of the "HOWTO" moniker, however, my searches for how to set the favicon in OpenWRT got me nowhere; so here it is for the next person.  I choose to reuse the luci radio icon from the wifi page for my favicon.  Feel free to use other images, although my first couple attempts using actual 16x16 icons did not work.  However, the stock PNG for the radio icon worked very well.

SSH into your router, and do the following:

cp /www/luci-static/resources/icons/wifi.png /www/favicon.ico

Generates this:

It doesn't get more simple than that.