I'm interested in information about changing ELMAH's UI. I know its possible, either through the ErrorLogPageFactory (not much info about it out there) or by rolling your own.
In short, I'm interested in the built-in facilities of ELMAH for skinning the report UI. Secondary is how to use ELMAH's API to roll your own UI (rather than the naive route where you write against sql or xml, depending on the storage provider your website uses currently).
Elmah has an ErrorLog.css file (inside the dll) that would be your source for skinning the report to your liking. I doubt it would be too hard to make that an external dependency. Further changes to the UI would likely require you messing with the source. It's good code, so that shouldn't be too hard.
The other item that I found interesting for pulling information from Elmah is that she (can I refer to software as an entity...) has an option for json output. The URL just tacks on a json element:
http://www.domain.com/elmah.axd/json?id=C8E40775-C215-4148-9D5E-6F865B4BCB9D