Android - How can I change the naming convention of the stock camera/gallery app?

That is not currently possible on the stock camera application, however there is an open ticket with the Android project team to make such an option exposed. http://code.google.com/p/android/issues/detail?id=10561

Meanwhile you can try some custom camera applications like "Camera Folders" which allows custom file name conventions in addition to folder groupings.

https://market.android.com/details?id=com.phasip.camerafolders&feature=search_result#?t=W251bGwsMSwxLDEsImNvbS5waGFzaXAuY2FtZXJhZm9sZGVycyJd

I would use Vignette. It will let you change the naming convention in the settings. The pictures end up in your gallery so no need to go searching for them.

You can either have new camera app which gives you in required naming convention or use filenamer and rename pictures.

Option 1: Camera 360 has this naming convention 2011-12-12-0215-4-20.jpg - https://market.android.com/details?id=vStudio.Android.Camera360

Option 2: Try this re.*(Renamer) which accepts regular expression for rename - https://market.android.com/details?id=com.dnsdojo.mokkouyou.android.renamer