Try replacing your src with ng-src for more info see the documentation:
Using Angular markup like {{hash}} in a src attribute doesn’t work
right: The browser will fetch from the URL with the literal text
{{hash}} until Angular replaces the expression inside {{hash}}. The
ngSrc directive solves this problem.
<div ng-controller="Cont">
<img ng-src="https://stackoverflow.com/questions/12922509/{{imageSource}}">
</div>