So now the question is, "Huh?" That is, about the copyright. At least in
the US, it shouldn't make any difference if you are embedding or linking
the picture. If the picture is yours, and you are trying to protect it,
it is SLIGHTLY safer if it is embedded, but it is so easy to get the
picture out of PowerPoint, that it is not much protection. If you are
using someone else's picture under fair use, it should make no
difference, but you should look at the Fair Use Guidelines for
Educational Multimedia. Here is one link:

http://www.utsystem.edu/OGC/IntellectualProperty/ccmcguid.htm

Finally, if you are using a copyrighted picture with permission of the
copyright holder, then, if the copyright holder said to embed in order
for you to have permission, then embed.

--David