Yep! That's the way you've got to do it. When I start a community pack, everyone knows that nearly a 3rd of the media will be done by me, and yes I always post WIP's of stuff I'm adding.
If you want a sucessful comminty pack to take off, you have to be one of, if not "the" main contributor to the project.
And trust me, It entails a lot more than just throwing everything in a folder and posting a download. You need to try and make sure that everything works (which is a real pain sometimes, because; even if it may work on your PC, does'nt mean it will work on everyone elses).
You have to make icons, and any other files that may be needed to get it all working, and visible in the editor, as well as check all file paths, and shader assignments, etc. And when you have a good sized pack going, say 2-300 pieces of media, it can really fry your brain after a few weeks. It's not a quick and easy job.
I do it for the the good folks here on these forums, not for myself. If I need anything for a game project, I just make it as I go myself.
The community packs are a means of bringing a group of people together, that have different talants to offer, to create something special for everyone, Not to generate media for game making in general.
So, if you really want to start a community project, and are prepared for the nearly overwhelming task of getting it all together for the good of the community, you need to get cracking, and show what you are willing to give selflessly to others.
Good luck, and if this gets off the ground, I'll probably join in myself.
2.5ghz QuadCore,4gb ram,1gb ATI graphics. Dual OS. WinXP, Win7.