I'll be honest - I'm currently lax at my posting at the moment, and I am totally to blame for it.
I think one of the major problems is simply a lack of enthusiasm - there's nothing really to attract new people's attention, or to keep people here. Of course, things in real life are also a problem, such as exams, or summer holidays, or other things like that cause a lack of activity on the site. I can't really suggest anything to remedy that other than patience - Maybe things will pick up later in the year?
All I suppose I can suggest is to try and advertise some more on different sites, such as other Transformers Roleplay sites, or big forums such as The Bolter and Chainsword
(a huge Warhammer 40'000 forum), or maybe some official forums such as IGN, Playstation, etc. I can't really suggest anything else.
Either that, or leave the site running, take a break and come back later, leaving the site in others' (hopefully) capable hands.
One thing you could do is some form of continuing competition, one in which the parameters keep changing, so it doesn't fall into the slump that the IDW Writing Comp did. So, what could happen is during one month (or whatever the length of time for it is) it becomes a writing competition, then a drawing one the next, then poetry, and so on and so forth.
It it, as always, up to you, Big Man.