That's about 25 gallons (US). Think is consider nano quah, which is typically ranged from 5 - 20 G.

To me the vital important thing is the water, equipments are mean to ease our maint work and also keep the water quality better and consistent.
Without a skimmer doesn't mean aquarium no go, just that you probably have to change water very frequent.

How about something to hang on your tank back? There are such devices mean to save space.

Experienced reefers consider nano tank need substantial skills and knowledge to keep them.
chk this site out for setup of a nano tank, http://www.nano-reef.com/
chk out the info, got many useful info for starters like you.

As about fishes, chk this out:
http://www.liveaquaria.com/product/categ.cfm?pcatid=15
the category of marine fishes for begginers and nano will be good for you too.

HTH