There are several file extensions that can be uploaded to BLoSCWiki, with the most common being .JPG and .PNG. .PNG files are preferable due to its lossless data compression. Avoid .JPG files unless absolutely necessary.
Every non-free image is used on BLoSCWiki under the auspices of the fair use doctrine of the United States Fair use law. This means that they are used for informational/educational purposes, meant to identify the subject of an article and to illustrate something directly relevant to the text in its immediate vicinity.
Given the nature of copyrighted images, BLoSCWiki tries to use them sparingly, and whenever possible on more than one single article, instead of using different pictures to illustrate the same subject.
The use of too many images on the same article should also be avoided. Apart from the general consensus that it causes aesthetic problems, this practice also directly challenges the policy that we use images sparingly.
Users may use up to three copyrighted images on their user pages as long as those are already being used on articles.