In the Arrow season 3 starting and ending intro, the Arrowhead got changed from plain to thicker one with symbols embodied on it, as depicted below
Is there any deep meaning/symbolism behind those symbols or is it just for styling?
It was a nod to the later episodes, The arrowhead was similar to the stencil used for branding him by Ra's al Ghul , below is the side by side comparison:
There were instances in season 3 where the logo got changed to something else:
In season 3 episode 7 "Draw Back Your bow" the title arrowhead logo was that of Cupid's heart shape arrow. In season 3 episode 8 "The Brave and The Bold" Lightning was added to the logo as the Flash guest starred. In season 3 episode 14 "The Return" the arrowhead logo reverted to the season 2 arrowhead when Slade Wilson returned. - IMDb
This trend was continued for the 4th season