It is working. Look at my gallery tag at this plugin.
But in the current version I don’t use the tag place. I implement the function in the pre block.
In the past I released it at the tag part.
Here the commit-Level with the old API.
And here the solution for the splitting (‘image_gallery’ is the tag name).
$images = explode(",", $tag->attr('image_gallery'));
The result is a array with the images.
By the way, I should look at the toolkit. Really nice features. 