Thanks for answering, but still doesn't works. In that post says to adjust Z axis, but when doing that it still shows what I said:
background [atlas: 1, z: 0, depth: 0]
button [atlas: 1, z: -10, depth: 0]
image [atlas: 2, z: -5, depth: 0]
Even varying depth on the inspector in play mode doesn't works... I've also read I could use different panels, but is that the only way to solve it?