Even if no mourners are present in Shul, Kaddish deRabannan should be said; preferably by someone who has lost a parent, but it can also be said by someone with both parents alive. Also, the last Kaddish should be said, either by someone who has lost a parent, or by someone who is quite sure that his parents will not mind.
There is a well-known minhag to light a Menorah on Chanukah in Shul. This is because of the pirsum ness which takes place there. However,the placement of the Menorah, both where in the Shul and the direction of the neiros, are patterned after the menorah in the Beis Hamikdash. Another reminder of what our Botei Keneisiyos mean to us.