The hero always gives the people the key to civilization. Both Osiris and Gilgamesh are culture heroes, the difference is that the Egyptians supposedly get eternal life, and Gilgamesh and the Mesopotamians never do. The key to Gilgamesh's success is a small plant he traveled long and hard for, eventually swimming (more like sinking really) to the bottom of a forbidden sea to get, only to have it eaten by a snake on the way back to land. The Egyptians constantly revel in their knowledge of immortality. Although reserved for pharaohs, many temples and tombs have hieroglyphs that cast spells and charm the body for preparation into eternal life. Also, there is the simple fact that each pharaoh's tomb was laden with things he was to take with him to the next life. Literally all of his possessions, even carvings meant to act as servants, were placed in the tomb. On the Mesopotamian side, most art gives thanks to a god, or glorifies the cultures greatness by showing depictions of everlasting peace, or of trouncing enemies, like in the Standard of Ur witch shows peace on one side, and a war that is being won on the other.
It is interesting to see how art differs between cultures. It's almost strange to see that many cultures have basically the same stories and they come up with completely different art. For instance, the Standard of Ur uses semi precious stones and shell cut into relief to depict two different scenes. (One on each side) It also uses three registrations, or strips of work, to tell the story of each scene. (Read bottom to top, left to right) All the figures in the piece are roughly the same size, and some are clothed, some aren't. It depends on which side you"re looking at. One side seems to depict the might of Ur and its army and king, the other tells the tale of the peace that Ur knew, possibly through the might of its army and ruler. It is said that this may have been a battle standard.