The Deathwatch army is the only army that I am using entirely custom bases. I started doing this because Deathwatch was never supposed to be more than 10 models. It started as the old White Dwarf formation from a thousand years ago. The army expanded a little when Deathwatch RPG picks up and I get excited and want to make another mini. With the release of the Deathwatch Codex and the Overkill box, this handfull of minis is going to expand to a full army. As it expands, I decided to carry forth the custom bases that look like deck plating or alien stuff.
I think the bases in the picture are from Secret Weapon Minis from the Tau Ceti range and from and Steel Invasion.
I made the choice to continue using 25 mm bases rather than the new 30 mm bases for consistency sake. I am old school and the new larger bases just look silly to me.