The beer map is like a spoke card i think. They are pretty cool to look at when you are riding along, and if you have someone behind you i have been told they look good when they go round.
The leather strap is there to proctect the top when getting on or off, to cover the decals and to stop the top tube hitting a vital bit on a man body when doing rear wheel skids.
Thats if i remember right.
I once made up a cyclechat spoke card with the logo and had it in my spoke fo a while, it was a good thing to watch in the shadow or to look down on when i was going. The wheel never seemed to be going as fast as i thought.
Its a styling thing. The spoke cards came from alleycat races or something so the riders didnt have numbers on them and they could be indentified when the bike was stopped. Search it on wikipedia. There are some cool designs about, its a messenger thing i think.