Descobri isso
find . -name "*.andnav" -exec rename -v 's/\.andnav$/\.tile/i' {} \;
./0/0.png.andnav renamed as ./0/0.png.tile
./0/1.png.andnav renamed as ./0/1.png.tile
./1/0.png.andnav renamed as ./1/0.png.tile
./1/1.png.andnav renamed as ./1/1.png.tile
claro, remova o -v quando estiver fazendo, ou perderá tempo exibindo todos os arquivos