It is common to use real world vehicles as inspiration for creating new fictional ones, even in science-fiction settings, such as Warhammer 40,000. While Games Workshop today probably tries to build all models mostly from scratch (just based on their previous designs, so there's the sense of evolution and familiarity), on the early days it seems they used real world tanks.
First, let's take a look at the M113 APC (Armoured PErsonnel Carrier), a tank born in 1962 but still in use at least until 2019!
Now let's compare it with Warhammer 40,000 Rhino APC MK.I and MK.II models:
As you can easily see, it's not only that the general armoured vehicle form is the same, it's that the threads are almost exactly the same (actually in the old MK.I model they are), in MK.II they changed them to that eagle-like design), the lights are pretty similar, and even the upper turret dispositions and back door is equal.
There are of course some changes, like side doors and exhaust pipes, and the side design has a more triangular shape compared with a parallelogram shape of the M113A.
The Rhino MK.II model became a bit more different with its changes to appear more sturdy, more reinforced than the original Rhino, but still the influence is there.
And really there's not much else, I just found a real tank photo and thought it would be worth to document the visual comparison. If I have time I'll research from which real life models the Leman Russ and Land Raider tanks come, as I believe both have military counterparts.