Yoshihiro Togashi (冨樫 義博) Artさんのイラストまとめ

HxH Chapter 371 Cover (and also the uncovered art)

HxH Chapter 5 Cover

Level E Chapter 11 Cover

Found a textless version!

Commemorative Intro Color Page from Chapter 255

HxH Chapter 350 Cover. And also just the Kurapika art from it.

Watercolor Paintings of Koenma, Keiko, and Botan from the YYH Art Book again

This art of Genthru is on a variant of the cover of the 7th Shueisha Jump Remix. I couldn't find the full art anywhere else (Jump Remixes' art are always samples from some pre-existing thing), but it seems it was also used for the cover of Weekly Shōnen Jump #1738, No. 26
(2003).

Here's the cover of Ookami Nante Kowakunai!! (I'm Not Afraid of the Wolf!!) and the chapter covers of chapters 1 and 4. As well as another illustration placed right before chapter 1. This was Togashi's first officially published tankobon volume.