The very frightful feature of Google Blogs is that Picasa usually compress your JPEG images without asking you.
The result is more than annoying: a file around 20KB with grey background and pixels corrupted and screaming out from pain.
The only way-out is to use PNG-images, but they usually formidable in size (around 1MB).
PNG-shrinkers fight this problem (type "png shrink" in google).
I have been using https://tinypng.com/ in last 2 months and it is very good (see the statistics on the picture).
The PNG-shrinking is rather addictive, once you use it, you will always shrink all you PNG-files.
But don't forget that this is only for WEB. For example, for colour printer and photo paper, you must avoid PNG-shrink, because it will seriously corrupt the quality of the image.
