Some good news...
The 'Public' account is now appearing in my test wave.
I added it to my contact list.
There is now text stating "Everyone has access to this wave."
[wave id="googlewave.com!w+NcOxJo8SW" server="https://wave.google.com/wave/"] worked when I put it into my post.
The bad news...
I switched out the wave id with my test wave and it did not load anything.
Here is what I have:
[wave id="googlewave.com!w+BrKwHWkEMW" server="https://wave.google.com/wave/"]
The default appearance is a bright green background for me (in FF, Chrome, and Safari) - anyone else? If this is the default, could it be changed to white?
WAIT... It is now working.
Per a comment on the wave you posted here is what I had to do. "substituting + for %252B" not just "%252"
Here is my working code:
[wave id="googlewave.com!w+rKwHWkEMW" color="#000000" bgcolor="#cccccc" font="Arial, Helvetica, sans-serif" server="https://wave.google.com/wave/"]
I tried using the Wavr button and could not get it to work with the appropriate information. Strange. Replacing the wave id got things working after I removed the 'B' in the wave id.
I hope this helps.