When you get Images by tag you get all kind of images. For example if you get Images by a tag you can get a image that is used as a presentation for a Club and the club is tagged with the tag you're search for. Is there any way to get only images in galleries by tag?
The tag system is unaware of where the images belong, so the quick answer is no. By using the methoed GetTaggedItems you can get images that are tagged a certain way, but you cannot limit it to just check images from a certain image gallery set.