A Full List Of Seedbox Providers
Here is a list of all the seedbox providers that have been in business for more than a year:

Andy10gbit
Bytesized Hosting
Canvyy
Chmuranet
CloudBoxes.io
Dediseedbox
EvoSeedbox
Feral Hosting
Hyperboxes
Pulsed Media
RapidSeedbox
Seedbox.io
The Seedbox Company
Seedboxes.cc
Seedhost
Seedit4.me
Swizzin
UltraSeedbox
WalkerServers
WhatBox
Xirvik
Bytesized Hosting, Netherlands / Luxembourg (thanks, /u/IceSeeYou!)

Chmuranet, Netherlands.

EvoSeedbox, Netherlands.

Feral Hosting, Netherlands.

Pulsed Media, France and Finland.

Rapid Seedbox, not stated AFAICT.

Seedbox.io, France, Romania, Netherlands, Germany.

SeedboxBay, France.

Seedboxco.net, Netherlands.

Seedboxes.cc, Netherlands.

Seedhost.eu, Netherlands.

SeedStorm, US and Netherlands.

SeedStuff.ca, France, Canada, and UK.

Tuvix, France and Netherlands.

Ultra Seedbox, Netherlands.

Whatbox, US and Netherlands.

Wicked Servers / tal0ne, France Netherlands, Germany, USA, Canada and France (thanks, /u/MAGNEFiK!).
Big Slice Box (Canada)
Bytesized Hosting (Luxembourd/Netherlands)
Dentoo (?)
Fibre Networks (US or Netherlands)
GBox (?)
GGSHQ (US)
My First Seedbox (Britain)
OnlySavvy (US)
Pulsed Media (Finland)
Rapid Seedbox (Europe (France, Netherlands))
Seedbox.me (Britain)
Seed Cafe (US)
Seedbox.gr (?)
Seedbox.st (Germany)
Seedhost.eu (Netherlands)
Seedbox Hosting (Multiple)
Seedm8 (?)
Seed My Box (France)
SeedStorm (US)
Super Seedbox (Luxembourg)
Super-Seed (Britain)
Super Seeder (Britain/France)
The Seedbox Company (Britain)
Torrent Swift (?)
Ultra Seedbox (Multiple)
WhatBox (Multiple)
Your Seedbox (Belgium)
Xirvik Servers (Multiple)
X0Host (Britain)