I'm interested in possibly changing the role of the religion in Githyanki society and thought up a nifty potential article for handling it.
Githyanki and the Divine
Up until recently, the Githyanki were a society that had no gods. Living in the Astral Plane, they tended to view the Powers with a decided ambivalence. Seeing the corpses of so many gods was enough to convince most Githyanki that they were not beings worthy of reverence. This atheistic bent amongst the species was encouraged by the line of Vlaakith whom insisted that only they were worthy of worship. The Vlaakith queens were unable to eliminate the reverence for Gith herself and often found her name useful in rallying the race.
The destruction of the Vlaakith line has left the Githyanki bereft of leadership and a small segment has decided to turn to the Powers for guidance. A great deal of these supplicants are nakedly self-serving in their motivation. Experience has taught the Githyanki that while the gods are mortal and fallible, they are still very powerful and any edge in the Civil War might be a worthwhile one. Of these supplicants; a few have genuinely discovered a love for religion and started attempts at converting their fellow Githyanki.
The most commonly worshiped power amongst the Githyanki is Tiamat. The long association of the Dragon Queen with the race and her ties to Gith's legend have made the transition of worship easier. Most of Tiamat's worshipers presently come from the Duthka'gith and this is probably going to hamper the spread of the faith in the long run. Most Githyanki view the union of Gith blood with Dragons to be an abomination rather than the 'blessed union' that the Duthka'gith preach.
Vlaakith's followers, being naturally inclined to supplication already, have found themselves gravitating to religion as well. The majority of them are far too devoted to Vlaakith's memory to take up the path of priest themselves but they recognize that being allied with 'other' gods will make her restoration more easy. A number of them have made pacts with human priests of Vecna, Wee Jass, Nerull along with other powers of Death and Magic. Some of these priests have even managed to pass along their teachings onto the lesser ranks of the soldiery. If Vlaakith isn't brought back soon, it's likely some of her servants may end up taking the path of the priest instead.
The remainder of the Githyanki that practice religion are almost always doing it on an individual basis. These Githyanki have encountered gods on their trips to Other Planes, particularly the Prime Material, and decided that any edge in battle is to be exploited. Most other Githyanki scoff at the idea that prayers will allow a warriors to fight better but the psychological advantage alone has given some pause. These worshipers tend to, unsurprisingly to Gods of War or Psionics. Evil Gods like Hextor and Bane are the most popular but there's even be a few Githyanki that have started worshiping Lawful Good Powers like Pelor or Bahamut. The later god has become especially popular amongst Gith that believe Tiamat may have done something with their legendary founder.
The majority of the Githyanki continue to view Powers as beings that are only relevant to their lives so long as they provide something to stand on in the Astral. The cult of Gith, however, remains strong and if she ever arose as a Power herself then she'd find the entirety of the Githyanki race rallying around her. That might be, more than anything, what could mend the fractured state of Githyanki society.
I'll toss out some opinions also.
OK, prior to the death of Vlaakith:
It is canonically OK for githyanki to hire barbarian priests as mercenaries, simply because githyanki are painfully aware of the fact that they're constantly short on healers. Living on the Astral Plane (most of the time), wounds do not heal naturally, either.
Prior to Vlaakith's death, worshipping any god is a huge no-no and drives the Revered Queen nuts. Any githyanki priests were renegades.
Now on to the opinions:
I think that the vast majority of githyanki would not go suddenly worshipping barbarian gods, even for the sake of power. They just don't have the mindset for it. They wipe their boots on the corpses of dead gods on a daily basis. I would go so far as to say that even post-Vlaakith, most githyanki with priest levels would be regarded as traitors.
In my own mind, at least one Githyanki term for a priest would translate to "heathen god-slave."
That said, a small number of renegade githyanki have been priests of this god or that for a long time. I agree that Tiamat would be the most likely choice of a (true) deity to worship (and might be more acceptable than other choices). They especially are not likely to start worshipping some vile barbarian deity (such as a human deity).
BoGr Guide to Missile Combat:
1) Equip a bow or crossbow.
2) Roll a natural 1 on d20.
3) ?????
4) Profit!