Let's say on an e-commerce site that sells unique pens, on a particular pen's product page, the image of the pen has an alt tag of "unique red-striped pen"... and another product has "unique blue-spotted pen", etc. The key words across all products being "unique" and "pen", which would also be helpful when it comes to SEO. However, if the person just goes to the general "unique pens" category page and sees a list of thumbnail images, each with the words "unique" and "pen" in the alt tag, would that potentially have a negative impact with regards to SEO by having the words too many times?