I wanted to create a party based on the characters my friends decided and two of them give me free hand for theirs so I wanted to ask you how to finish party.
So far we have
Half-Elf Bard NG (either normal or Jester)
Elf Mage
Dwarf Barbarian CG

I would tend myself to Pala, and for my friends a Tempus Cleric and a Neutral Half-Orc Fighter-Thief but I wanted to ask you if you see any potential for improvement of those which are not already fix?

Go with what you tend to. Your selection looks fine, but the most important thing is it's YOUR game, not somebody else's. If you go with what other people say, it's not your party. Do it. Go with it...

He might be playing a multiplayer game, hence the other characters being "fixed". In any case, OP, you have the four basic roles filled already (warrior, wizard, priest and rogue), and the Bard serves to provide additional spellcasting and support via Bard Song. A Paladin is a fine choice as a secondary melee tank/bruiser who can also provide some backup healing and spell support once they reach higher levels.

It's not required, but a Ranger has a neat little additional ability in IWD called "Tracking" that's usable as many times as you want. Every time you use it, you glean a little extra info about the map you're in (although you're unable to track in cities and some dungeons) that will give you hints about the monsters that you'll face and sometimes a rough idea of where they might be. If this is your first ever playthrough of IWD, it can help give an increased "tabletop feel" when you're going in blind.