This is a simple, and very tidy way of hiding things in a variant, either main or mobile.

Arrange all your images how you want them, then hop into our variant. I'm presuming Flexible Block, but the same idea will apply to Freestyle Blocks.
Expand the Page & Layer Gallery > Mouse Off > Web Block > FlexGroup.
Select the image you don't want to show and click the 'Visible' icon to make it red (hidden). The other images will rush in to fill the gap, but not affect the other variant.