Besides eating local hawker food, visiting the multi-racial temples and Penang Hill, visiting each site for mural paintings and steel rod sculptures is also a very fun activity. There are a few ways to do this, so it's either by walking which can be very tedious or riding on a bicycle or taking a trishaw to go around from one place to another. Steel rod sculptures can be easily located but mural painting can be a bit hidden from the main street despite you get on the correct street by using the map. So don't hesitate to ask the locals for direction if you can't find! =)
Map can be downloaded from here: http://www.tourismpenang.net.my/pdf/street-art-brochure.pdf
So make sure that you pay them a visit before they are being destroyed because most of them are not well maintained.
Enjoy and have a nice day!