a) Copy the BMP file you want to use to iGO/content/userdata/usericon
b) Massage your KML as follows--just below the header telling what version of Google Earth KML add the following:
<name>(the name of your POI here as you want it to appear in iGO)</name>
<metadata><igoicon><filename>content\userdata\usericon\(poi BMP name.bmp)</filename></igoicon></metadata>
c) Add your KML files to /iGO/content/userdata/poi
UPOI Editor will do this automagically, and for large sets of POIs at that--and it exports cleanly to KML that iGO will take natively, so I think we're fixed
Suggestions for icons--you'll need to do them in BMP format, 40x40 would appear to be the practical limit if the big "icon stacks" out of a standard branding.gro or data.gro file are anything to go by, though a lot of these are 32x32. Nmollet's PNG icons for Google Maps converted to BMP (http://mapicons.nicolasmollet.com/
) work quite well in iGO once KML files have the appropriate headers, and these are just straight BMP conversions from a 32x37 PNG file.