This is too suspicious, not formatted URL for just an image... of course, it won't pass.
The most suspicious part is that the URL doesn't end with an image extension.
It doesn't end with .jpeg, it ends with regular .jpg; but even if it would end with .jpeg, it's allowed.
What you see in this abnormally long part in the URL, is kind of virtual or even physical folders structure. If you analyze it carefully, you will see it has a lot of internal folders separated by slash; and this path, finally, leads to 2013_BOG-1.jpg ('jpeg' appears to be folder's name); BUT after this filename, there is another string of params added, consisting of some encoded string and the 'size' var.
Obviously, any image you refer in miniBB, should end with an extension and should not have any kind of params or vars followed after. This is a security rule. I guess, if you just provide the URL ending with extension (removing the params part), it should work.
I.e. it should be this URL:
Or, if it will not, then it's not possible to insert such an image in miniBB.