Aliasing Tesso → Gweek
Link to alias

Reason:

Same artist. Goes by "Tesso" on FurAffinity. "Gweek/GW" appears to be the artist's preferred name, as suggested by Pixiv and Twitter usernames. The tag GW was only used on post #280784, so I assumed that between Gweek and GW, Gweek would be preferred.

http://www.pixiv.net/member.php?id=6943
https://twitter.com/GWGW
http://www.gweek.jp/ (though apparently an empty site)

Proof:
-Profiles on Pixiv and FurAffinity both link to Gweek.jp

-Tesso FA uploads also in the Gweek/GW Pixiv gallery.

http://www.furaffinity.net/view/6416922/
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=21444729

http://www.furaffinity.net/view/10120724/
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=34169978

http://www.furaffinity.net/view/1037971/
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=378148

http://www.furaffinity.net/view/1434615/
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=1271604

http://www.furaffinity.net/view/944476/
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=244897

http://www.furaffinity.net/view/4635833/
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=13903464

And more.

Verified and approved

I'm leaving gw as is since it seems like it might get tagged for multiple things (guild_wars, namely) but probably not commonly enough to warrant disambiguation.