Not near Inverness, but you can always try your hand with the rockart right by Bernera Bridge (which you will be very familiar with by the end of your hols!) - http://www.themodernantiquarian.com/site/8410/barraglom.html, or the excellent Rubha Charnain ones down in Harris - http://www.themodernantiquarian.com/site/8408/rubha_charnain.html
G x