WordPress MU

Forgive my greenness.

So I've installed MU (subdomain-style not subdir)...created my first Blog...edited a default theme to my liking...and exported said theme for use on Blogs #2, 3, 4, etc.

Now, is it possible to edit the theme files (php, css, images) on a blog-by-blog basis? Or are theme edits now only possible across all blogs using said theme?

More practically, if the theme used to style the blogs has an image of, say, a frog in the header and I want to change the frog to an image of a donkey on Blog 2 (but not on any other blogs using this theme), is this possible?

If so, where can I edit these files? I can't seem to find them on my server, etc...

thank you

All blogs share the same set of themes you've activated at SiteAdmin-->Themes.

If you leave a theme inactive, you can then assign it to individual blogs at SiteAdmin-->Blogs-->Edit

Changes to a certain theme will affect all blogs using that theme. No new theme files are created when a new blog is created, so whatever themes are in wp-content/themes, are all there is. You can have zillions of themes, though, so go ahead and dupe your favorite theme folder, tweak it, rename it, repeat.

Oh, you can add a custom header options page to your theme, http://ryan.boren.me/2007/01/07/custom-image-header-api/

I'll give that a look. Thank you, sir.