Some things can't be rotated because Microsoft doesn't know how to control
it. Try the following:
1. Insert your clip art image on your slide
2. Right-click the image, select "Grouping", and click "Ungroup".
3. When asked to convert the object, click "Yes" (or OK)
4. Try rotating it now.
By the way, you can immediately regroup all the objects and it should be
able to be rotated. You can also ungroup everything (in most cases with
clip art), then select individual objects and change their colors, etc.
Unfortunately, this doesn't usually work with JPEGs. You will need to do
this in a graphics program, like Microsoft Photo Editor, etc. then bring it
into PowerPoint.
Have fun!
