Ooooh gorgeous ornate! I'd love to have one, but they get too big for a 75 gallon.
If you go the bichir route, like I said before, go with
a Senegal
An albino senegal (next on my list of bichirs to get)
A delhezi (next on my list, after I get an albino sen, this one has pretty good coloration)
Or one of the palmas species
Palmas palmas
Palmas polli
Palmas buettikoferi (this one has gorgeous coloration!)
I was going to suggest rope fish (they look like little snakes, I adore them so darn much!)
as well (they are a polypterus, just like bichirs), my only concern is that they have the potential to get ~2ft, which in a 75 gallon, wouldn't be a whole lot of room to swim when it's only 18" in diameter. I would want a 5 foot tank that's at least 2 feet wide to have them, along with the fact that they like to be in a group and are EXCELLENT escape artists, although some people keep them in smaller tanks, I always like to go bigger!
As for the spiny eels, you could do
zig zag eel (macrognathus circumcinctus) max size 6-8" (get at least 2, they like company of their own kind)
Macrognathus pancalus (I believe they like to be kept in the company of either each other, or another peaceful spiny eel species, max size 8")
Or a good ole peacock eel (max size 12")
