TShock provides a more configurable "message-of-the-day" (MOTD) system than the Terraria experience has by default. The "message-of-the-day" is displayed to users when the run the /motd command or when they join the server for the first time. You can configure this by adjusting the motd.txt file in the tshock configuration folder (near config.json). You can also use the /reload command to reload this configuration file after it has been changed, while the server is running.
The default message-of-the-day is this:
Welcome to [c/ffff00:%map%] on [c/7ddff8:T][c/81dbf6:S][c/86d7f4:h][c/8ad3f3:o][c/8ecef1:c][c/93caef:k] for [c/55d284:T][c/62d27a:e][c/6fd16f:r][c/7cd165:r][c/89d15a:a][c/95d150:r][c/a4d145:i][c/b1d03b:a].
[c/FFFFFF:Online players (%onlineplayers%/%serverslots%):] [c/FFFF00:%players%]
Type [c/55D284:%specifier%][c/62D27A:h][c/6FD16F:e][c/7CD165:l][c/89D15A:p] for a list of commands.
The following tokens are available for use in the MOTD:
%map%- The name of the current map%onlineplayers%- The number of players currently online%players%- A comma-separated list of players currently online%serverslots%- The number of slots on the server%specifier%- The command specifier (e.g./or.)
In addition, the Terraria color codes are supported. These are RGB colors in brackets. For example, [c/FF0000:Red] will display the word "Red" in red. Terraria chat tags are clientside rendered, meaning that they can be used too, even if more tags are added, without explicit TShock support.