I just figured out something that I should have figured out long ago. But never late then never.
The problem was that I just couldn't figure out why the thumbnails of my images always seemed darker on Dreamstime. I thought it was something in way DT processed the images, but other contributors didn't seem to have this problem.
I use a color calibration device on my monitor. And I export into sRGB as suggested. But still my thumbnails always seemed darker than what I was developing in Adobe Lightroom or Adobe Photoshop.
The solution I discovered was that LR and PS are color managed programs while the browsers used to view web pages are not always color managed.
"Color management is the technique of achieving consistent colors across various imaging-devices. So, whether you are editing the photograph in Photoshop or viewing the same photograph on your cellphone or printing it out on paper — it should look the same on all media. However in reality there’s quite a difference when you view the same image on your PC and on your TV. Achieving color-consistency calls for color-management awareness."
Enabling color management in Google Chrome occurs not in the browser options but in the launching of the browser. Here is how to do it:
1. Right-click Google Chrome desktop shortcut and select Properties.
2. Append ––enable-monitor-profile to the path in the Target field and click OK.
Here is a image of what it should look like: LINK
Some other browsers such as newer versions of FireFox and Safari are already color managed and don't need enabling.
The lesson for myself is to view the thumbnails in several different browsers. I'd love to hear from others and their experiences with color management.