Problems ranking images

[realmaverick]

Out of 30,000 daily visits to one of my websites, zero comes from Google images. Yet my website is image-centric and has several hundred thousand of them.

At present the images are all stored on a subdomain of the main domain. That domain doesn't receive links. Links are always pointed to the full page. So I guess the subdomain is pretty much powerless.

Visiting the subdomain alone, downloads a file with an extension .part1. I don't know whether that matters or even why its setup that way. Our server admin company set it all up.

Each image has an optimised alt tag but doesn't have optimised image names.

It just seems odd, that we get no image traffic at all. I searched the subdomain in google images and some images do show up, along with their alt texts.

On the main gallery, we also use lazy loader, I don't know whether that could effect SEO negatively, I didn't think so, but perhaps worth mentioning.

Any thoughts on what could be the biggest issue with ranking these images?

[tedster]

I don't think serving images from a dedicated sub-domain could be the core of the problem. Doing it that way is a best practice recommended for improving page load speed because it allows browser to open more http connections in parallel.

The only other thought I have is to as if each image has a good caption and if so, is it marked up clearly as being semantically related to the image itself.

[realmaverick]

Yes, optimisation is the primary reason we use a sub domain for images.

The images don't currently have captions, only alt text. Would it be of benefit to add a caption, similar to the alt text, under the image? In a gallery environment, I think dynamically adding captions could lead to a lot of duplication of the word "widget". Leaving the keyword off, would put the image out of context, hmm.

Though on the single page, it will be fine.