Well icons of any kind are avoided in Judaism, as far as worship goes, although that's not to say there won't be decorative symbols on the walls or even stained glass, none of this is really connected to worship and a synagogue could just as easily be a room with bare walls. There are a few things that would probably be present in a synagogue. One is the ner tamid, the eternal light, which is above the ark. This is a reminder of the eish tamid, the eternal fire which always burned inside the Beit HaMikdash.
There is also the ark itself which holds the Torah scroll/s. The scroll is made the old fashioned way by a scribe called a sofer.
There's also the tallit or prayer shawl which is only of value because of the fringes on the four corners and the tefillin and worn usually just in the morning or phylacteries which are the leather boxes containing parchment with scripture that are strapped to the arm and worn on the head on weekday mornings.
I can't think of anything else that looks different. Some Jews rock when they pray. There's some bowing. And services are all or mostly in Hebrew. None of the things I've mentioned above could really be considered icons though.
Dauer