Actually inline css should be avoided but in this case it makes sense. Inline css also has always priority overriding css file rules. Disadvantage is of course that no one can set custom styles but that is probably not needed for this effect.

Otherwise the theme_head filter would be the way.

I think you should ignore stopdesign. As acrylian has said, it is a very complex, special theme. The developers also find that they cannot support all extensions on that theme as well.

As to the thumbnails, they are implemnted as background images which may make your mouse-over stuff impossible. It is actually the "frame" that is the image.

Actually it could be possible to add the support for Stopdesign, adding the proper selector in js file, but then is not easy to deal with the text-indent rule. The plugin puts the zoomed image inside the tag [b]a[/b], to have the same link of the corresponding thumb to image page, but the text-indent rule moves the zoomed image out of the screen.
I could add a temporary jquery css rule to override text-indent while the zoom is visible or may be add a specific rule for "a" tag inside my container...

I was also trying to add support for translation, using gettext_pl() function, but I was not able to get it work.
I've compiled the .mo file for italian language, putted .po and .mo files in the locale folder inside my plugin folder, but no way to see the translation.
Btw in the documentation (http://www.zenphoto.org/news/translating-tutorial#plugin-translation) is missing an important info, that I found in functions-i18n.php. Beside the text to be translated, also the name of the plugin is required by the function:
gettext_pl('some text','plugin name')

Thanks for the note! The translation tutorial indeed is missing that info.

Eureka!
The file .mo has to have the same name of the plugin!
This info is missing too in the tutorial, or may be it's not so clear..
Now the translation works!

That actually was there once for sure! Somehow my last edit has killed the formatting of the example completely, too. Fixed now. Thanks for letting us know again.

You are welcome acrylian, I know how hard are you working on this project, with a very few people constantly engaged in the development. Any time I can give a little help I'm really very glad.
The couple of hours I spent, figuring out how to get the plugin translation working, now make sense, because this will save time to other people.

Thanks. Let us know in case you find anything more or unclear descriptions (hopefully not that much...;-)).

I've added the support for Stopdesign, quite tricky for several reasons. Of course, as sbillard said, the mouse over effect can't be associated with the images (because they are backgrounds) but with their container. Anyway it's not a big difference for users I suppose.

Now I'm writing the documentation and download page on my site, but I'm having problems with the download manager (download list plugin) of Zenphoto.

For some reason the downloaded file provided by PrintDownloadLink function is corrupted, while the same file, downloaded via a direct link in the address bar of the browser, is ok.

I've tried .zip and .tar files, and also .jpg and .pdf files to make a check.
The strange think is that only pdf files are downloaded correctly, while the other 3 formats are leading to corrupted files.

Any idea about the reason?

Now comes the most strange think I discovered:

I've downloaded 2 small zip files, one with the link provided by PrintDownloadLink, the other one with a link I manually added to my page, pointing directly to the file.

Then I've opened both files with a text editor (notepad++) and, surprise, the first file as a blank line at the very beginning, that the other (working) file has not.

More: once I deleted the blank line in notepad++ and saved the corrupted file, it was no more corrupted!