So I've had an experiment, well at least started an experiment to get me into the marsh frame of mind to then develop my fimir properly. Firstly I covered part of the base in filler in an abstract kind of pattern to begin to represent the slopping mud, leaving some 'holes' to become pools of water.
Next I used some 'ultramarine blue' paint on the water parts and 'blackfire earth' (from the citadel textured paint range - first time I've used it and, whilst I'm not sure what I was expecting it to be like to use, I certainly didn't expect it as it was) to cover the filler and start to build the marshy earth.
A very liberal wash of 'coelia greenshade' over everything has helped to get the basis of a nice dark rotten green look to everything.
This is as far as I got today (as I was mainly focusing on painting some of my Black Templars seeing as I'm currently playing a 40k campaign). Plenty left to do - drybrushing the mud to pick out the texture, add some static grass in a few tufts, and pour in some water effect. Here's hoping that the scenic base will look pretty good and really help boost the whole visual theme of the fimir.
Those of you with eagle-eyes will have noticed that I have modelled a cavalry base rather than an infantry base - well, the fimir aren't the only things in the marshes!