Well this is some news! More concept art about the enemies in Rise of Lyric has been found, some known, and some unknown! Check them out here!
Also, there's more to Sonic Boom than meets the eye in the development perspective...
Both Rise of Lyric and Shattered Crystal were once called Sonic Synergy! This was what the title screen looked like:
This name was first coined in a website for Edward Moore. In his site, this diagram for both games were shown:
It shows both versions in which you gain power ups. Look closely here and you'll find Super Sonic on the 3DS version. Either he was supposed to be unlockable but was scrapped, or maybe he was used as a reference for the screen. Here's another diagram with Rise of Lyric in it, showing the multiplayer event. The full size ishere :
There's also concepts for the Multiplayer. Here's the design for the "Results" and "Select Hero" selection:
In both images, there is a change in the design of the characters (except Tails), most importantly Sonic. He has less spiky quills, tan arms, and his main quills are longer. It bears a resemblence to Modern!Sonic. And Amy also has a small purplish pink scarf. her purple stockings are longer too! Knuckles's shoes are a bit simular to Modern!Knuckles's shoes, having those steel plates.
What do you think of the title change, the character change, do you think ROL and SC would be better with these changes?
UPDATE: There's a few more concept arts! Here's one of Shadow, and he looks creepy.