SVG is ideal for some cases, but if you will create modules/templates to edit in Content Editor, you will use image field to the cliente/user upload the image when edit page with this template created.
JPG is good for banners or big images because is more lighter;
PNG is good when you need transparency background in image, how icons for example.
Tip: if you use Photoshop, save the images with the "Export to web" option. It helps in their weight.