The transitions are done via a grey scale noise mask( or an image that fades from black to white in some way ), I have included a link where you can find several of these images in the plugins help file ^^ but you can also simply search images for "grey scale transition masks" and you should find plenty of results, alternatively you can find transitions masks in a lot of rpg maker forums, under resources for rpg maker XP and VX, they should be labeled as "battle transitions" or something along these lines. :)