I had a little present for my dad, and the gift bag I had just wasn't cutting it. So I got some markers and stickers and set my kiddos loose.
I would recommend using permanent markers if the bag has a glossy finish like this one, or use a matte finish if you're going to use regular markers. This took a long time to dry with regular markers, but the kids had fun making it.
Grandparents always seem to like something that shows the kids are actually involved in the gift giving, and this really fit the bill. My dad was very pleased with his gift and with the packaging it came in!