Histamine derivatives are not fun because the histamine receptor is not as nearly as "fun" as DA/NE/SER.
Compare alpha-methyl histamine - (???) with alpha-methyl-tryptamine/phenethylamine... both are powerful psychostimulants.
The problem is, histamine receptors control things like immune system response, gastric acid secretion, wakefulness, but as far as we know they don't really have a "central" effect.
Also, the old monoamine theory that dopamine = confidence and serotonin = happiness is a total crock of shit, there are too many factors involved to correlate a mood and a neurotransmitter.