Extending a CCK field formatter I've created a custom formatter (display) for filefield but I'd like to add a settings page per field for width and height.

Currently my code only consists of the bare minimum to get the formatter to work (which it does). However I'm currently hardcoding width and height at the hook_theme() level.

I've not found any examples of setting pages for formatters only for custom fields. I suspect that it's not possible to do this for a formatter and I'd have to define my own field rather than formatter. I could create a global admin page and loop through all fields and set the settings as a variable but that might become an issue when upgrading it to 7.

Any feedback or ideas would be great.
D7 has this baked into the field formatters. You could look at how that is done and emulate it. But I suspect that would be quite a lot of work. How far off is D7 for you? It could be worth waiting till then to allow field settings.