I'd recommend a 'coffee and cream' look. So, if the shirt is dark brown, add a lighter brown jumper (or vice versa). However a shot of colour, as suggested by Mamya would also be a good idea. You need a warm colour (such as red, maroon or - if you're feeling bold - orange) to go with what you've got.
Do you all seriously think grey and brown match when worn together? Each are ok separately but not together! I would go mad if OH wore that combination of colours but thinking about it he would probably go ahead and wear them anyway as he has no colour sense!
ok, i'll admit, on the duck it looks ok (ps it made me laugh a lot that to illustrate fashion advice you showed a picture of a duck), but the tracksuit???? Just because poeple and designers can put them together dosen't mean they should put them together!