The board of supervisors of each county may in their discretion maintain a good and sufficient fence around the courthouse yard, and, when necessary, a substantial pavement on the walks of the same, and may have shade trees planted therein, and shall provide for the absolute exclusion of all livestock therefrom. No tent or booth may be erected on the courthouse yard to be used for the advertising or the vending of any goods, wares, notions or nostrums, or for doing the business of a photographer, unless written authorization therefor is obtained from the board of supervisors. The board of supervisors may pave and improve the streets around the courthouse yard.