Leo:

I may be way off base, (since I am a novice at Symbiostock, WordPress, and PHP), but this looks a little bit unusual.

public function list_raster_sizes has a call to apply_filters('list_raster_sizes', $data)

public function list_eps has a call to apply_filters('list_eps', $row)

But

public function list_zip has a call to apply_filters('list_eps', $row)

Shouldn't it call apply_filters('list_zip', $row)

Forgive me if this is the way it should be.  It just looks a bit odd to me.