As an ME, with PE friends. The PE is primarily required for Civil Engineering and for those Mechanical Engineers who work on structures. Therefore a blank with something like this that with PE added would work for a female PE Civil Engineer.
https://0.s3.envato.com/files/102933467/sun 1.jpg
You are correct that States and Municipalities are primarily concerned about Civil Engineers stamping and certifying their structural designs.
However, there are many engineering disciplines and we get our degrees in those specific areas (Electrical, Chemical, Petroleum, Industrial, Aeronautics, Civil, Mechanical, etc.) - most of which generally fall under the broader categories of Electrical, Mechanical, Civil & Chemical. Laws and regulations concerning the practice of engineering are regulated by the individual states. I can't speak for any other state, but here in Texas, you can only call yourself an engineer and offer engineering services if you are a registered PE. Once you have that registration, there are no restrictions on the type of engineering that you can practice or the types of designs, studies or drawings that you can certify. It is up to the individual engineer to ethically represent himself as being sufficiently knowledgeable and experienced to certify the accuracy and validity of anything that he attaches his seal to.
I only practice electrical engineering and the nature of my work does not often require a formal seal, but occasionally I do have to stamp and certify some of my designs and studies. Sometimes it is for state-related work, but usually it's just a requirement of our clients as assurance that the work done for them was performed by a qualified engineer.
Anyway, a simple symbol like calipers with PE lettering might be adequate for many, but I want something that more broadly encompasses at least the 4 major fields of Civil, Mechanical, Electrical & Chemical. I think that would have a wider appeal to more engineers. I just haven't come up with a combination of symbols that looks good together yet.