nice

Assalamoalaikum,there is this hadith that states that one who prays for showing off has committed shirk, now apparently this applies to all forms of worship. There are people who act all nice to others for the sake of getting something from them or to misguide them or to lie about their abilities.Since acting nice to others is also a form of worship, i wanted to know that such decieving of people lie in the same category of shirk?

I recently read that one of the signs of the Hereafter is that people will compete in the building of mosques.Does this mean that we should not build nice mosques.  What about the wonderful and beautiful mosques which are so appreciated for their architecture and art?I also heard that there is a hadith that a mosque should built only to have a roof ad to keep the rain out.  What is the authenthicity of this hadith?Also many times in our Islamic school as part of art class, the students were asked to design mosques, and the best one would get an award, is this wrong also?