I use my online Google drive to source pictures I want to include in my posts.
A little fiddling is required ...
Set the photo sharing to 'anybody can view'
Copy the shareable link
The URL will look something like this
https://drive.google.com/file/d/0B5KuQk ... sp=sharing
The file ID for this photo is: 0B5KuQk2b_F-VdVBpUVd1RDdCN1E
-- delete the stuff after the file ID
-- After 'google.com/', replace 'file/d/' with uc?id=
Ending up with
https://drive.google.com/uc?id=0B5KuQk2 ... Vd1RDdCN1E
This is the URL to paste between the IMG tags obtained by clicking on the 'Img' button in the edit box toolbar. I find it least annoying to paste the raw link in between the img tags and then edit the URL inline.
