On this wiki, images must conform to Speculative Evolution Wiki:Media Copyright Control, as well as Speculative Evolution Wiki:Manual of Style#Images. This page details when uploading images is appropriate, and which images are allowed.
Generally, uploading files which are completely unrelated to speculative evolution is not allowed. This can be broken in rare scenarios, but in general a random forum image of a random TV show is not allowed, especially without licensing, as may be the case.
Forum images are not completely disallowed however, for example, images of animal skeletons or an Indonesian rainforest are okay with licensing. Then there are borderline images of speculative animals which look like Pokémon. These images are usually never allowed in forum posts, but on user pages they are acceptable with permission.
A better option to display off topic images is to use an external link to the image. This can be done with wikitext in the format
[http://www.example.com/ text to display].
The majority of images should be on topic article images. In articles, anything the slightest bit off topic will most likely be removed. Then there are other images which function as backgrounds, badges, etc. These usually conform to the rules of user page images.
With all of the "usually" and "most likely" comments, I must note that there are exceptions, and these exceptions must be dealt with by logic, not by the strict requirements of this page.
Thank you for your cooperation.