I think that title almost explains it. What is best for SEO to use in section Recommended products for alt and title attributes of thumb images? Should they maybe be empty? Recomendded products are show on a page where one main product is opened, below main product in slider (as seen in most web shops).
I think I know why your asking this question, as if you add alt attribute to a related product, its different to the product on the actual page, so what SEO value is it going to bring to the page? Perhaps you should think about it from a usability point of view, rather than an SEO point of view.
The image alt attribute is used to describe an image when the image cannot be rendered. It is also used by 'screen reader' software where the content of the website is read out aloud, usually for users who's sighting is impaired. (and yes Google does also read the attribute)
So the alt attribute should be descriptive of the actual image. In this case I might also add'Recommended Product' to it:
<img src="blue-widgets.jpg" alt="Recommended Product: A Blue widget">
How ever if you are worried about it being unrelated to the actual page, you could just leave it off.
The title attribute is used to add extra information about an element and is often shown as a pop up tool tip when mousing over an element. The title attribute doesn't carry any weight with Google - However keyword stuffing it could have negative effects.
Sp the title might be:
<img src="blue-widgets.jpg" title="Click here to see our Blue Widgets page">
SO if you used both it might look like:
<img src="blue-widgets.jpg" alt="Recommended Product: A Blue widget" title="Click here to see our Blue Widgets page">
Title attribute for IMAGE is not used as a factor in search engines algorithm and image alt attribute has really little importance, see here 2013 Search Engine Ranking Factors : http://moz.com/blog/ranking-factors-2013