The FW Medusa is an excellent ingame choice, but more importantly the model is great. Whilst a pain to put together (there are large resin components that don't sit well with the plastic chassis!), the end result is a nice pseudo-real-world tank. I really like this Armageddon version, which comes with a enclosed crew compartment.
I used basic sponge weathering to dab on paint chips and these were then highlighted by hand. The lower track sections were weathered with MIG weathering powders.
The paint scheme was Cadian because at the time I was considering doing a Cadian army. Whilst I bought a few units, the idea never took off. However, since then I've painted up a few Cadian Guard tanks - they work well as "auxiliaries" for most Guard armies.