ok I have found a way to make things work
1-take the tga from dominions1(europa.tga for example) and put it in the \map directory
2-make a copy of aran.map and rename it to europa.map
3-open europa.map with a text editor
4-change theses lines:
#dom2title Aran
#imagefile aran.tga
To these(Europa should be the name of your tga file):
#dom2title Europa
#imagefile europa.tga
5-You could change other things there (like description for example) but that's not the point
6-let's not change the rest
we'll change it later from inside dominions 2
7-well it's finished simply load your map within the editor (but now the most hard work awaits you: you have to redo all neigbours !!!!)
PS: for those of you who said it's difficult to convert to dominions2, I must say
(joke inside
)