when u use cross epg u will see the radio logo....
that's what u see with my enigma 2 box...
the location for the radio logo is as someone already seid
/usr/share/enigma2/Radio.mvi
delete the old radio.mvi then transfer the new one..
if it still dosent work may be the image u are using dosent allow u to change it...
however I have never had this prob before...