You need to look over your guest-list and consider the people coming. Also have "back-up" plans - have stuff ready to pull out if it gets dull, like board games, cards, vcd/dvds, dbox/console games, and then think of stuff like truth n dare, charades, etc. Can mahjong, but it will change the entire feel of the party

Definitely music, etc. Also there can be lots of things in preparations: food/drinks, decorations, and other creative things. The last party I had was almost 10 years ago, but it still kicked a$$. I had music, food & drinks, dance area, dart board area, I put on videos (on mute cuz music playing), put giant blank white paper on one wall, with pens hanging so ppl could leave markz, msgs, sketch, had furniture in one room all to side so room to dance.
Here it really depends on the location too...my last party I had access to use outside area too, so we had a rubbish bin-fire, n guitar playing, volleyball, etc. even brought sofa downstairs outside lol..
dunno - just be creative - n actually think n plan n research a lil bit...parties can be absolutely dull n boring or better than a pub/dance club, or however you wanna make it.