If it's your cup of tea go for it, personally I don't like them except on lowered and loud drag bikes, but everyone has their own aesthetic that they like.
As far as lowering resale value, it will, but not necessarily due to the racing/stunting image, having been a stunter in a past life I can say that long swingarms make it very hard to get the front up by comparison to a shorter one, if anything it would speak volumes about a bike not having been stunted.
That said if it is part of an overall "customized" bike it can raise the value as well, many many show bikes go for the long swingarm/low front look and they don't seem to sell for less, however any mods done to a bike to increase it's retail are likely in vain as almost everyone has their own idea of what a given bike should be.