Don't make solid interface from 90s style. FOnline is real time multiplayer PvP game, which means the interface must take as least pixels on the screen as possible. Be transparent, if possible. And must be white by default with an ability to change color to whatever player wants. Don't forget about color blind people or people, who just can't stand certain color. Because game features real time combat and PvP, every pixel on the screen covered with useless interface element (solid background) is decreasing player's field of view and thus gives advantage to those, who use custom interface. Don't waste your time on useless solid interface with metal parts, which will be immediately replaced by the modders. PvP players were always the best interface designers, ask them to make one. Just make sure it's monocolor and can be recolored either through the options or by downloading them and overwriting.