Is it problematic if for now we adopt a "report any signatures you find distracting" policy? I agree that that signature in particular is distracting, but I also think that there's value in relatively unobtrusive images in signatures. The forum is not yet sentient, but I am, and if you show me something obnoxious via the (confidential) reporting system I will get it taken care of.
In the meantime I limited both signature image height and font size. They are both fairly generous limits and therefore compliance is not necessarily acceptable, but non-compliance is certainly unacceptable.