Looking at the front page of your site, the majority f images that are not ssl are the little specification bars
srren size / mp / ram / battery etc.
http://qmart.pk/image/Mi%20Xiaomi/Mi%20 ... note-4.jpg
http://qmart.pk/image/Accessories/JBL%2 ... jbl-go.jpg
http://qmart.pk/image/MacBook%20Air/App ... K-GGF2.jpg
I am not familiar with that theme, but it seems that the way these specification 'bars' have been inserted under the product name is the main part of the problem. It may be that functionality is not ssl aware and so does not attempt to make the link secure but more likely is that it stores the full url to the image and those images were added before you made the site ssl.
You can try to delete and re-add one of those images to test this (just to one first to make sure it works).
If so, you can either delete and re-add them all manually, or locate where those images are stored in the database and change them using sql.
The fact that most images are ssl suggest that the ssl part now works okay, its that theme or some added functionality that does not handle ssl properly.
The way opencart stores paths and the best way to do it is to be stored relative so
image/path/image.png
NOT
http://qmart.pk/image/path/image.png
but if your theme expects the full url you have to get them all changed like I suggest.