Switchplates come in single, double or even triple switch sizes.  Switchplates larger than this are available, but harder to find or have to be custom made.  The double and the single are the most common.  There are also more modern switches where the switches are larger called GFCI/Rocker switches, these do not fit the standard toggle light switch plates, so it is important to make sure that the switch opening is the right size.  Whatever the switch plate is called, you should be able to tell if it fits your switch by the picture.

Some switchplates are made by hand using a découpage technique. Art prints, which have been cropped to size, are mounted on each durable steel plate by hand with waterproof adhesive. These plates typically have an acrylic sealer. The screw is often hand-painted to match the background of the switchplate.  I don't know about the quality of these plates.   Most ceramic or similiar manufactured plates are typically of higher quality.

             

The Guardian Angels are much different! The plate is installed over a regular 2 outlet plug in place of the plate that is already there. Then each outlet has a snap-on cap that clips right over almost any plugged in device! This is great because the devide can't be unpugged meaning we can protect our children when a lamp or other electrical device IS plugged in. Of course the cap can be snapped on if nothing is plugged in also.

The caps are easy enough for an adult to squeeze to unplug something or plug something in. They're only available in beige but if it proects my grandchild, who cares? Search for Guardian Angel Outlet Covers by looking in Baby Safety & health / Outlet Covers.