I would like to know the original artist for all of these, if he/she is known at all!

WHAT. This doesn't make any sense.

The artist is an unknown Toshiaki, I believe.

Ah, I thought so. Ah well.

Should've posted the translation notes too. You can dig them out here: http://cerealandmilk.net/iichan/img/res/543.html

Also, the artist is "that guy who only draws Homeo 4-koma on img", in his own words.

What board on img? img /b/?

"img" means "Nijiura on img". Same for "dat", "may" and "nov". Any other boards are referred to by their normal names.