If you use our Easygoi editor to create your email or design your form, any picture you add to the layout will be automatically resized to fit.
To make the pic smaller, simply click on it and use the left-hand panel to reduce its width and adjust the horizontal aligment.
To make it bigger, you can't do the same, as Easygoi won't allow an image to be larger than its surrounding layout (it would break if it did). No worries, though. Just drag the picture to somewhere else big enough in your layout to hold the pic size you want and then adjust it accordingly.