All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and messenger.
There are narrations that indicate that when a person sneezes, he should say 'Al-Hamdu Lillaah' or 'Al-Hamdu Lillaah Rabb-il-‘Aalameen'; all this is permissible.
Ali narrated that the Prophet said: “If someone among you sneezes, he should say ‘Al-Hamdu Lillaahi Rabb-il-‘Aalameen’ and the person next to him should say to him ‘Yarhamuka Allaah (may Allaah have mercy upon you)’, and then he [the sneezing person] should say: ‘Yahdeekumul-laahu wa Yuslihu Baalakum (may Allaah guide you and rectify your affairs).” [Ahmad - Shu‘ayb Al-Arnaa’oot graded it as Hasan (good)]
As regards wearing new clothes on the day of ‘Eed, this is not an obligation, but a person should wear the best clothes he has and should beautify himself for this day. Also, there is nothing wrong with you wearing those clothes before the day of ‘Eed and then wearing them again on the day of ‘Eed as long as they are clean in a way by which the purpose of beautification and adornment that is required for the day of ‘Eed is fulfilled. For more benefit, please refer to Fatwa 129787.
Allaah Knows best.