I have a question similar to this one here but with circumstances that are a bit different.
I purchased a logo from a seller online through Fiverr a few months ago. Since then I have incorporated this logo in various areas and have spent a lot of money on it. Unbeknownst to me, a large part of it includes a stock graph they found online. I found this out after doing a reverse image search of the graphic online. I traced that stock image to multiple stock photo websites and a lot of them mention that their content can't be used for logos or trademarks, which was my whole intent when purchasing a logo.
Could I still use the logo I bought and trademark it in the US granted that the seller had made some revisions to the stock photo he found?
Here's all of the relevant info I have:
- The seller had changed up some parts of the stock image, this includes color scheme, orientation, and made the picture look a little low poly. 
- The original artist of the stock photo is based in Russia and as far as I can see there is no registered copyright on it and don't think they could apply for US copyright anyway. 
- While I'm not sure where the seller (located in Pakistan) officially downloaded the logo, I had nothing to do with the final design of it or downloaded anything from a stock photo website myself, so I'm not sure if I'd be bound by any terms of the stock photo website 
- The stock image is very niche and a bit random. Across all the websites the artist has published it on, it has about 5 or 6 downloads altogether. 
- As far the copyright of the seller's work goes, the Fiverr terms state that buyers have all the copyright, though I don't know if this is nullified by the use of the stock image. 
 
     
    