Hi I'd like to know if we are allowed to place google ads on a page where there are only displayed some images (of course, without making them look like they are associated with the ads in any way) thanks
Images only could be a problem, not from a TOS point of view but from a technical one. AdSense is a contextual service - it requires some text on the page to target ads correctly. I recommend placing at least a caption with each image. It should be fine.
Adsense doesn't necessarily need text on the page. It can also read Meta tags and title tags, as well as display ads relevant to the domain
Images are content. It's allowed. So it's OK, but if you want relevent ads make sure you have alt tags on your images and site meta tags and all that good stuff, the bot will read those.