What do these kanji mean: 吉庆有余
吉, short for 吉祥, lucky, auspicious, propitious
庆, short for 喜庆, joyful, happy event, to celebrate
有余, to have enough and to spare, to have a surplus

to have a lot of happy things

In some Chinese traditional paintings, you may see a plump child holding a halberd(戟, ji3, similar with 吉), a chime stone(磬, qing4, same with 庆) and a fish(鱼, yu2, same with 余), usually a cyprinoid, sometimes only a fish and a lotus flower, which indicates 吉庆有余.