Where are you wanting the images to link to? Google shouldn’t have an issue crawling your attachment pages unless you’ve asked them not to (using a robots.txt file).
I don’t think it needs to be linked to anything since it’s just a product picture. I’m always under the impression linking to attachment page helps with SEO. But I haven’t modified anything that I know of in terms of asking for nocrawl.
What’s you recommendation on the image linking in my case?