Off centre drains for showers are very common ... almost all of the ones we do (unless they are square) are off centre. We mainly use the Schluter Kerdi shower kit system, but there are several options.
http://www.schluter.com/8_4_kerdi_shower_kit.aspx
One of the important aspects of the install is to ensure that the lip around the perimeter of the shower pan is at the same elevation so that the tile on the wall starts at the same height. This shower kit is made to go in place of a bath tub i.e. where a bath tub is being replaced by a walk-in shower.
The slope between the drain and the wall where the faucet is will be slightly steeper than the rest of the shower floor because it has to cover the same vertical rise in a far shorter distance (basic geometry), but unless you're pinned to the wall (oohh errr Mrs) that's not somewhere you normally stand so I have never encountered this as being a problem.
Another important aspect of a shower tray such as this is that you need to use smaller mosaic tile in your design for the floor as it has to be able to follow the contour ... ideally 2"x2" or smaller. Watch for glass mosaic though as many are not rated for supporting a persons weight.
There is another option which is a linear drain ... like a trough basically. A big advantage is that you have one continual slope towards the drain (which goes across the whole width of the shower pan) so you can use larger format tiles as they don't have to follow a curved 'bowl' shape as in the other method. However this type of install has other complexities and is not typically for the budget minded. There's another guy on here from BC who can tell you all you want to know about linear drains if interested.
I have attached an example of a Schluter shower nearing completion so you can see how the position of the drain and the slope of the floor looks ... it's only steep enough to allow water to drain, not so steep that you feel like falling forward.
Linear Mode
