I am playing in a 600 point DC build. This is my team I was looking for some feedback

D17-004 Booster Gold
016 Super-Man
002 Jericho
016 Batman Beyond
004 Terra
004 Green Lantern

This is what I have
WIZKIDS DC
D17-004 Booster Gold

REBIRTH
001 Deathstroke
002 Jericho
004 Terra
006 Power Girl
008 Adeline Kane
012 Aqualad
013 Cyborg
015 Wonder Woman
016 Super-Man
023a Steel
025 Phobos
028 Tempest
031 Batman
100 Mr. Terrific

BATMAN: THE ANIMATED SERIES
006 Alfred
008 Two-Face
010 Ninja
016 Batman Beyond
019 Alfred
030 J-Man
031 Poison Ivy
040 Batman
S001 Batarang

BLACKEST NIGHT
004 Green Lantern

Firstly, welcome to Heroclix! A tip for posting teams on the forums: There's a [ team ] function you can use to cleanly display your team in a way that we can just click on the characters to see them. Quote my message to see.

Force Build 11983533 0
Set	#	Name	Team	Pts	Value
WKD	D17-004	Booster Gold		75	SELL
RE	016	Super-Man		150	SELL
RE	002	Jericho		60	SELL
BTAS	016	Batman Beyond		100	SELL
RE	004	Terra		65	SELL
EW	004	Green Lantern		55	SELL
Force Total:				505	$0.00

As you can see, this puts you at 505, so you have plenty of room. Based on what you have here: Green Lantern really doesn't work for you here. Literally your entire team has , so he won't be able to carry anyone. I kind of dislike Jericho here as well, since he doesn't have much impact for a 600 point game. I would basically suggest removing those two, and in their place, RE Batman and Deathstroke would be great additions. Batman provides solid support while also being a threat, and Deathstroke is an amazing threat. Alfred can fill in the points well enough to support Batman, but you could be forgiven for wanting a Ninja, instead.

Force Build 11983533 1
Set	#	Name	Team	Pts	Value
WKD	D17-004	Booster Gold		75	SELL
RE	016	Super-Man		150	SELL
BTAS	016	Batman Beyond		100	SELL
RE	004	Terra		65	SELL
RE	001	Deathstroke		100	SELL
RE	031	Batman		85	SELL
BTAS	019	Alfred		25	SELL
Force Total:				600	$0.00

The roles we have here
Super-Man: Main threat
Batman Beyond: Secondary threat and Stealth-killer
Deathstroke: Secondary threat, devoting 350 points of your team to offensive pieces
Batman: General support with Outwit, Outsiders, and Incapacitate. Tertiary threat if you need it.
Booster Gold: Call-in counter and Probability Control. Decent utility to have, especially on a bigger team where you're likely to find chunkier figures and more actions are available. Certainly can make some attacks, but try to keep him in back.
Terra: Telekinesis, Barrier, perhaps some stat buffs. You could realistically make barriers next to your target while a flier like Super-Man carries her up for a Charge. Damage buff through Empower, defense buff through her trait. Dedicated support piece for sure. Enough of a threat that you're not out of the game if you're down to her, but she's much more useful as support in this game.
Alfred: Point-filler, but a stealthy Perplex is always nice. Extra benefits for helping Terry and especially Bruce helps, too. You could even consider pushing him a couple times to turn him into a healer.

All told, this would bring some good threats as well as good support to prop them up. If you want a bit more threat, you could trade Terra & Alred for Steel as you group your team together for his defense buff. Tempest can also be extremely useful with a free water-smoke that can do some nasty things, but including him would likely make your points a bit short.