What to highlight... everything?
Before you start to highlight, those washes are pretty strong. Perhaps take some of the base colour that you washed over and paint again, leaving the recesses (real and imagined) washed as they are. It\'s a general rule with washing, that you put the base colour down, do your wash, and then your base colour again to neaten up the wash.
Then to highlight, take some elf flesh (or a suitably light flesh) and go over his knuckles and the upper surfaces of his hands with it. The same with his nose, his bottom lip and his cheeks.
With a mixture of bone and white, do the tips of his horns, with more emphasis on the upper surfaces. Then just white on the extreme tips and upper edges.
For the armour, take some silver and drybrush that over his chainmail. The edges of the armour and helmet can get some chainmail. Over the bronze bits on his helmet, shining gold.
The axe gets some silver too - after a black wash. Streaking silver along the sharp edges emphasises the edges and makes them look sharper. The rivet on the axe can also be accentuated by a touch of silver on its upper surface.
His beard is very red, so you won\'t be able to highlight that with a light brown, so perhaps go with a fully red beard, and highlight it with blazing orange.
Well, that\'s a simple start - nothing amazing, and you, or others, will well have other ideas and colour choices. But me thinks that if you start off with those, the concepts behind highlighting will be a little more obvious to you.