В таблице перечислены все окончания, недокументированными являются последние три: g, r и _d.
Suffix
Name
Size, px
Keeps
Image
Proportions
Sample URL
Sample
Size
s
Small Square
90×90
No
i.imgur.com/fY37q5Ds.jpg4 KB
b
Big Square
160×160
No
i.imgur.com/fY37q5Db.jpg8 KB
t
Small Thumbnail
160×160
Yes
i.imgur.com/fY37q5Dt.jpg5 KB
m
Medium Thumbnail
320×320
Yes
i.imgur.com/fY37q5Dm.jpg16 KB
l
Large Thumbnail
640×640
Yes
i.imgur.com/fY37q5Dl.jpg49 KB
h
Huge Thumbnail
1024×1024
Yes
i.imgur.com/fY37q5Dh.jpg97 KB
g
?Giant Thumbnail?
1294×1294
Yes
i.imgur.com/fY37q5Dg.jpg109 KB
r
?Retina Thumbnail?
1456×1456
Yes
i.imgur.com/fY37q5Dr.jpg187 KB
_d
?Preview Thumbnail?
145×145
Yes
i.imgur.com/fY37q5D_d.jpg6 KB
Как? Reverse engineering, детка:
:: Set imgur image URL
set IMGURL=fY37q5D
:: Download image
wget https://i.imgur.com/%IMGURL%.jpg
:: Test all suffixes
for %%i in (a b c d e f g h i j k l m n o p q r s t u v w x y z) ^
do wget https://i.imgur.com/%IMGURL%%%i.jpg
for %%i in (a b c d e f g h i j k l m n o p q r s t u v w x y z) ^
do wget https://i.imgur.com/%IMGURL%_%%i.jpg
via
Imgur:
The Imgur API - Models - Image