wow.. brave.. so you have an automated function to get your contour layers? (as in each "color" is created automatically?) that's pretty cool, inkscape tends to crash so much on my comp i'm doubting it'd even load... I'd think there'd be many frantic saves and crashes.. or some kind of beefy comp involved in that...

Depending on the use of the map the wiki standard might not work quite as you want it to... What I mean is that that those colours are meant to make the map for maximum readibility for such things as road maps or city locations... this means your beautiful heightmap becomes more faded into the background, since it's not meant to be the focus of the map... for instance, in the screenshot the rivers pop-out much more than the elevations, cause as a google-maps-like webmap it's more imporant than elevation... like i said that can be a good or bad thing depending on what your trying to accomplish, if it's meant to be a travel map or to identify locations travel distances etc (much LIKE a google map) then it's perfect... if your trying to go for a dramatic map that shows more of the "3D qualities" of the map, making the topography pop a bit more might be beneficial...

that being said.. how to do that.. i'm not sure, i've been struggling with trying to create a heighmap style map into a fantasy art style map and it's always filled with a LOT of manual blending.. something which i'm sure would be difficult in your sense.. all i could think of is maybe making the mt elevations have a bit more contrast? i mean.. if you go from colour A -> B, making B a bit darker or something? I remember posting an article i found about swiss cartography standards.. it may be something to look at, they create unbelievable looking elevation maps in which the mts are detailed and pop, but at the same time the roads, rivers, and everything else don't dissapear... ooh! i found it! seems it's more for DEMs themselves.. i dunno you could try to glean something from it...