I think I'd call him Schatz (bad sound but sweet meaning) that is "trasure" (sentimental meaning as well as the common gold one) in German – his language –, or Pinguino ("penguin") because he really seems one, especially when wearing his concert suit. :) In Italy we most use "tesoro" ("treasure"), "amore" or "amore mio" ("love" or "my love"), and all those silly too sweet nicks couples seem to love, such as "orsetto/orsacchiotto" ("teddy bear"). A poetic one I really like is "luce dei miei occhi" ("light to my eyes"), but it's not much used for it's so long.

I call mine Aşkım This means my love in Turkish

Do you mean nicknames for your boyfriend or girlfriend? Well the common one I can think of is Honey but some couples say hubby and wifey.