As Topic/Message does not support attached, one of the options could be to use custom attributes for Topic entity to link uploaded images to the forum topic. Then you need to manage image galleries for particular forum yourself (creating gallery, uploading images, creating thumbnails, etc).
Some intro to relief work with custom attributes could be found here - http://world.episerver.com/Blogs/Valdis-Iljuconoks/Dates/2012/2/Synchronize-Relate-entitys-attributes-in-a-strongly-typed-way/.
It's not supporting List<T> attributes for now, but could be easily added if really required.
We have EPiServer CMS 6 R2 along with EPiServer Commuity and Relate Plus. Also we have built an ASP.NET web site with a forum on top of it (the forum is using the community and relate APIs). There is a request that each forum topic and its replies have multiple file attachments (documents, images and videos). Since I am new to EpiServer, can someone please let me know how can I implement this?
In my newtopic.aspx file I have some text boxes only that receives the subject, body and other details then creates an instance of ForumTopic entity and inserts it into the database.
Thanks a lot