Firstly, let me say hit to everyone here!

I'm a newbie and can't wait to hear all the knowledge that has been built up from members over the years!

My question is, I have developed my craft somewhat and feel that my current images are far better than the old ones I have listed.(Most of these old ones have a sale listing of 0.)

So what would you do, would you delete all the old non-selling images or keep them and try and keyword/title them better? They don't look amazing in my eyes but I have bad for your portfolio seo if you delete a ton of images (even though they are getting no interest) Other side of that is that I feel it would look far better with them gone!

Would welcome your opinions.

Thanks

From my point of view, you can't answer the question until you can see and judge for yourself whether your newer images have more sales potential than the old ones.

The stock agencies work like search engines. If you have something to offer, you have chances to be found. I assume that the search engines assign you a certain "value". If this value is zero, I think it will be difficult to make your new - possibly better - images findable.
So if the newer images have a much higher sales potential, I would delete the old data that led to the poor ranking of your portfolio.

But: my statement can be completely wrong, because I don't know the algorithms of the stock agencies.

They cost time and effort, so I let them be. Although some of them hurt my eyes. Now and again there is an unexpected sale. Not quite like the Vileda one mentioned above. Yet 
The only ones I did remove are some old calendars.

...My question is, I have developed my craft somewhat and feel that my current images are far better than the old ones I have listed....

With stock images, you have to keep reminding yourself that "better" is a function of usefulness to the buyer, not artistic merit or technical merit.

If your new images are selling, removing some " bad" old ones probably won't help the new ones sell more - most of the time, a prospective buyer will not see both side by side or rule you out because they saw one of the old "bad" images. It's a very pragmatic process - if the image works for what they're working on, they'll license it.

So if you see that you have missed a few important keywords on an old image (not stuffing the image with things that aren't relevant, but fixing omissions that you have since realized are important), edit the image at the sites that will let you. Once or twice I have updated an old image (mostly better post processing) but generally only used that when uploading to new agencies rather than replacing at existing agencies (and those days of new agencies popping up seem to be well behind us now).

None of the agencies will share all the rules about how they rank search results, but I'm not aware of any suggestions that having some old unsold images on the same subject hurts the rank of something new. Generally, getting a few sales soon after upload will help improve placement. The biggest thing you can do to influence that, other than having a well composed and looks-goood-in-the-thumbnail image, is to get really good at keywording. If the buyer can't find it, it doesn't matter how wonderful it is

It can be a bit embarrassing to look back at very early images, but it's amazing how sales of new images helps you overcome that

What about portfolio rating? The more slag and defectives in the portfolio, the lower the overall rating of the portfolio.

That is a good point. I think some agencies place a high value on how "efficient" a portfolio is.

On the other hand, all images build links to your port, when customers look at them or lightbox them in galleries. Plus the frustration if a customer wants to download a file and the file is no longer there.

And...agencies might not like it if people deactivate files. Some agencies don't let you delete at all, others only 10% over a certain time period.

So even a simple thing like should I delete old files, needs careful consideration.

Personally if there are some files that really irritate you, I would delete those.

But if you are not using your port as advertising toi attract working clients, I would just ignore and focus on new content.