Delaware's flag is an example of the common formula for US state flags: "We already came up with a state seal, why make more work for ourselves?" then just slapped the seal on a piece of cloth and ran it up the flagpole. Granted, Delaware at least uses colors other than the typical dark blue, but the seal on the center is far too busy:
A concept used on other blogs is the Betsy Ross test, meaning how simple it would be for someone who isn't a master embroiderer to sew together the flag. This flag fails, there is too much going on the middle, unless you're using those iron on decals or something.
Additionally, it gives the date of statehood right across the bottom. Delaware has one claim to fame, it was first, and their slogans, license plates, seal, flag, and I'd bet official stationary all make sure you remember that. I believe the Simpsons once hoped to see its famous screen-door factory, but what Delaware subsists on is "#1." Here is an example of a possible flag:
Boring, but more simple than the current design, and it would probably win in a referendum.
However, there is something else that sets Delaware apart, something that is less deserving of light-hearted mockery. Unlike any other colony, Delaware was begun by the Swedes. We have plenty of British colonies, a number of Spanish ones in the southwest and Florida, even a smattering of remnants of the French and Dutch Empires, but Delaware was the only Swedish colony on North America. Though not to the level of Jamestown, St. Augustine, or Plymouth, it's a milestone that deserves more attention.
To that end, I present my own suggestion. I've kept the background colors and the diamond shape because they are unique among state flags (and because it invokes the Brazilian flag, which is one of my favorites), but added something new to the center that, I think, better reflects Delaware's history than the current mish-mash:
(It's the flag of Sweden, just in case you were unsure)