Is there any risk in deleting some of the bad photos I previously posted?

Were they accepted or still under review? I’ve sold photos relatively recently that I uploaded over three years ago. There is really no need to remove assets that haven’t sold. 

If assets have been up for a year or more and never made a sale, there’s probably no harm in removing them.

Assets in your portfolio that are not in demand have no effect on search algorithm. Only popular assets have a role on how assets are shown. 
Yes, if you want you can delete them. But, is it really needed? Maybe they will sell.

First, this belongs in the Stock Contributor forum below where we discuss all matters related to Contributors.

https://community.adobe.com/questions-38

Second, there’s no reason to delete approved assets unless you have to for legal reasons.  Or your content violates Stock’s TERMS in some way.  

If your content is in demand & has good keywords, people will find it in keyword searches. If it’s not, they won’t.  It’s that simple.

Don’t try to second guess search algorithms. You’ll never succeed.  

Good luck.

is this a stock question?