Here is a project that I really got to get into. My client wanted an Imperial Knight that had turned to Tzeentch. It was to be allied with his Chaos Daemons force, so it did not need to be a Thousand Sons Knight.
There is only a little bit of conversion here- the head was swapped out for the head of a High Elf Phoenix. Otherwise, the alignment was all down to coloration.
I wend with a blue to purple fade for most of the armor plating- I felt this was right for the god of change, and the bright pink contrasted nicely with that (and also matched a force composed largely of pink horrors).
Of course, it isn’t right to leave any Imperial Knight mini without freehand, so I made sure to get a lot of the Changing God’s iconography all over him.