I want to upload pictures for my posts but everytime I have tries I get message "The extension XYZ is not allowed" XYZ being jpg, JPG, jepg, JPEG, png, PNG, tiff or TIFF

What extensions are allowed?

I can link pictures through URL but that means first uploading to another site or places like piccasa etc.

Sudev,

As of now, file upload is restricted to sharing word document or pdf files, mainly meant for sharing tech regs, SR's, results...etc.

For photo video sharing we will have to continue to use 3rd party hosting websites to ensure that the heavy multimedia does not slow down the performance of the forum. I mostly use:
youtube
imageshack.us
picasa