Hi Ryan,
Sure, either way works properly. Please note you could of done the same thing by using args.FieldName within the ImageMerging handler as well.
Regarding the images not scaling properly, I suggest you use the img.Width and img.Height properties, and then calcuating the new size by scaling them by a constant. i.e builder.InsertImage(img, img.Width * 0.5, img.Height * 0.5);
Thanks,