using 1.61 i could add a image overlay to my video (i used a transparent PNG with a logo), this feature is not in the 1.70 version. was it removed? could you add it again?

We didn't delete the Logo system.

To add a logo image in your video:
Click "Settings" button under the Video tab of Bandicam, then check the "Add logo to video" under the "Logo" tab.