White Pixel Integration

Hello,
I made a web service to track whom opens the emails with white pixels. Which works perfectly. Now I would like to add this pixel to the emails in distribute survey and im a little stuck.
But how can I add piped text (identifier) like for example ${m://Email1} or an embedded field from contacts to each pixel. In this way I would like to identify whom opens the email and whom doesn't.

<img src="https://xxx/webservices/Flappy/pixel/project/${m://Email1}.gif" />

Thanks!