Hello, I actually found the solution to the problem not long after posting. I just get impatient sometimes. lol I do not know if you are having the same problem, but I will tell you how I resolved this, and hope your issue is similar.
In the past, I have found that these things usually lie with Google/ Google+ accounts. So, I went to our org. google account, which is linked to everything, including our youtube account.
There, I found that the account still had the old logo in our profile pic. When I changed it there, it resolved the problem.
If this doesn't resolve your problem, and I can help further please let me know. I will do my best to help you located the offending image. lol In the meantime, check all the places that you place you old logo. You may find the culprit. ^_^