Hi Satyr Studio,
the LAF does not charge for you making advertisements, however the banner ads are reserved to the current owner, North Star Miniatures.
You are welcome to open a running thread in the Commercial section for special events or anything that doesn't fit on the topical boards - a dedicated range of Fantasy figures would probably benefit from being posted to a thread on the Fantasy board, though, ideally using the [COMMERCIAL] tag in the title to indicate your vested interest.
Also, you are welcome to add an unobtrusive (i.e. not too big and NOT animated) banner to your signature.