@BasedPharaoh  
I have explained this on previous images of the undersides of the vehicles in my pony themed army.
 
When a vehicle is wrecked in-game, we flip them upside down so other models can use the wreck for cover. I originally did this for a bit of fun, and as an excuse to paint another picture on the models (on a panel that usually only sees a single colour, assuming the owner even bothers to paint their models at all…)
 
This usually has one of two effects.  
Either my opponent feels rotten for wrecking my vehicles, or they then try to wreck the whole lot so they can see the rest of the pictures.
 
Here’s the bulk of the force’s vehicles showing the underside pictures  
>>557558  
Spa twins whirlwind tank  
>>659241  
Derpy rhino I painted for one of my regular opponents  
>>666808  
Sonata Dusk rhino  
>>818080 Copied from >>861045  
Wasn’t as happy with my Aria one, so I never uploaded that.  
It’s based on this one I drew >>837992

really odd thing to have on the underside of your tank

Just realised I got the 1100th 40k crossover image slot on here.
 
Been a long time since I made note of a number on my uploads anywhere.
 
(Used to be on 4chan before I came here. Uploading images on 4chan became near impossible thanks to ‘Embedded file’ messages, plus they don’t allow anthro art there, some of which is exceptional. (And some disturbing, although little shocks me after browsing on here with no filters for over 2 years)).

Back door of this model is here >>885667
 
One of the side panels is here, although I have cleaned this up a touch since I took the picture. Mainly her eye, which has been bugging me ever since I uploaded the picture here. >>890740