Is there a pictograms repository under an open-commercial license? I'm looking for pictograms repositories for non-verbal people. I found two types: 


ones that I need to pay like PECS or SPC,
and others that are free but they have a no-commercial license like arasaac or PiktoPlus.


My question is: Is there a pictograms repository under an open license and that I could use its pictograms with commercial purposes?
I found one! http://straight-street.org/

Those pictos have a Creative Commons BY-SA license.