Other modules like the Devel module?
I believe devel generate uses a pattern like [FIELD_NAME]_devel_generate() when deciding who/what to ask for generated data, and then devel implements those functions itself for the core fields.

Unfortunately I don't really see a way to alter this behaviour as there is no Factory pattern or similar that one could use to instantiate derivative/overridden functionality.

What my team usually does is creating content more to our liking in the install profile. This allows us to gradually build in some basic content that the client will want anyway into the development process, and we use a variable to tag nids that won't be useful one we go live, so that we can easily remove the junk content.

If we stick with using devel, here's what I would do:


Hack the module. The code you are looking for is in devel/devel_generate, and then split up into many files, mostly one for each type of content it creates.
Make the functionality generally useful.
Post a patch in the issue queue saying. "I wanted to use devel like this instead, is there a way to incorporate this into Devel?".