No this is not about his face being on the mountain.

The second to last page we see minato holding his own kunai.
There was an emphasis on the kunai for some reason. is it the writing on it thats important?

http://www.narutobase.net/manga/Naruto/599/14

Why was he being remembered by kakashi at this time?

is minato there because he was the one that promoted kakashi to jounin?

thats what im guessing.