Solution: seems like the mk2-3-4 HR graphic for Storage tank haven't been done yet. I did them myself using PSP tonality regulation on original HD graphics (= hr-storage-tank.png).
I am not sure it's a bug actually ... might be some wrong setting ... i have this problem since 0.16 which i installed yesterday ... any idea? The icon in the inventory are correct for Storage tank 1-2-3-4 but when i place them on the ground i always get the same basic storage tank graphic (they still named 2,3,4 and their capacity are correct (25K,50K,75K, 100K) but still ... the graphic is always identical. Any idea?