Salmonberries and thimbleberries are actually two different berries but they are both relatives of blackberries and raspberries. I beleive people often mistakenly call thimbleberries salmonberries not knowing the difference.
Salmonberries are like a raspberry and are an orange color when ripe. They have a bitter sweet flavor that is ok but not great. They may be good in beer because the bitterness might complement the hops.
Thimbleberries are red in color and relatively flat like an acorn hat. In my opinion they have a similar but better flavor than raspberries but they are not quite as sweet and are very seedy. In a beer though it wouldn't matter if they were not super sweet because the sugars would ferment and the seeds would settle out. They are a lot of work to harvest though because you don't get many berries off of a single plant at the same time.