Baldur's Gate takes place in Faerun, I suggest using Faerunian creatures as other races. Also, be careful with adding races because each race gives different bonuses and penalties and certain races shouldn't be stronger than others without hefty level adjustments.

Here, check this out: http://www.d20srd.org/indexes/monsters.htm

There are several monsters in here that can be used as races.

Also, classes, since if this is a new BG game it should be off the 3.5 rules like Icewind Dale 2 was (well, 3.0 at the time). These should be your classes:

http://www.d20srd.org/indexes/classes.htm

Class kits don't exist in 3.5 because instead you have skills and feats for further customization:

http://www.d20srd.org/indexes/skills.htm

http://www.d20srd.org/indexes/feats.htm

And, base races and their bonuses are here, as well as other basic rule stuff:

http://www.d20srd.org/indexes/basics...escription.htm

There are several other classes that exist in supplements, but they aren't OGL (Open Game License) so I can't link to anything that has it. If I do find it though, I'll throw it up.