Is there anything in particular that has to be done to prevent a popout sig from having white speckles all around it?

It seems like any background that I use.. any style.. render.. etc etc, it always has white speckles once I save it as a .png

Any advice is appreciated.. thank you!

Save it as PNG-24, not PNG-8.

No can do. When I do this, it goes over the size limit. Is that the only way..?

Yes
If it goes over the limit, add a posterize filter and then adjust it so when you save it, the size will be lower