So you really need to ask why this mod is having trouble attracting the necessary people and retaining them? Most of the original staff have moved on leaving you and Raven more or less as caretakers.
For an answer, look to your public forum. Any burst of internal work by artists is not rewarded by publication on the external.
You need to attract talent, yet anyone who turns up won't be able to show off any work they do. It's a small point, but a vital one. It's not like you are Gearbox software and are paying a full time salary or anything. So what other ways can you pay the artist? Future fame? BWO has been stalled for so long that's an unlikely option.
This is an older topic but personally I'm not sure how much "showing off artwork" factors into an artist's decision to do a project. Yes it may be true for some people, but some people just want to accomplish a common goal. Some artists also just create stuff for the sake of creating not out of a need for public recognition. Maybe the typical artist does so here, I don't know.
That being said I do hope BWO gets out the door eventually in whatever form the creators choose to release it (and hopefully not one they feel they've been forced into doing). I know a number of other campaigns have had their original visions changed by the influx of new blood, and in my experience they've been lesser campaigns for it (WiH for example (yeah, I'm a heretic. I'm fine with that)).
Also I will admit to being guilty of one of those people who wanted to help but then didn't deliver. Then again, I don't deliver on a lot of my own personal artistic projects so in that regard I would not pin the blame on BWO but would put it solely on my own shoulders. If I ever get the creative urge I may try and lend a hand again. It's much simpler than trying to create a whole total conversion from scratch (as I've dreamt up a number of times).
In any case, BWO staff be true to your original vision! Naysayers be damned. That being said, trying to create buzz to inspire new talent may not be a bad thing either.