Just about any song can be sung a capella. I have been singing any and all types of traditional and contemporary folk songs without instruments for years. I think there is often too much reliance these days on instruments.
Of course, I accompany myself sometimes as well. Some of the songs I sing a capella include Frankie Armstrong numbers, old English Music Hall (Vaudeville) songs--even the odd Leon Rosselson song (like "We Sell Everything"-- a real challenge as an a acapella number.)
Just pick your favourite upbeat numbers and work out your own unique a capella arrangements for them. Have fun!