I'm going to supplement MonkeyHead's excellent synopsis with a few assessments of my own:
Douglas Alexander = Scottish Labour stalwart, slimy little patronising shitbag. Good-party-man. One of my least favourite people on the planet. Also, the more successful half of an abysmal brother/sister duo; he and his sister Wendy used to represent various parts of my home town (more like ruling them as petty fiefdoms) in the Scottish and British parliaments. Wendy led the Scottish Labour Party for one terrible year. She resigned in disgrace, leaving a trail of broken dreams behind her. Currently the Shadow Foreign Secretary. Take a look at his statements on the "special relationship" in recent days if you want to get an idea of what he'd be like.
Danny Alexander = Some kind of oversized, gormless mustelid that wriggled itself into a suit and began representing parts of rural Scotland for the Liberal Democrats. Chief of the Treasury. No real principles, parrots the party line, no charisma. Used to be the Secretary of State for Scotland (the representative of the British government in Scotland) until the government realised he was a liability and chose someone slightly more personable. No idea what he'd be like as a foreign secretary, he's very much an economics man.
Andrew Mitchell = Disgraced Tory chief whip. Alleged to have called a police officer a "pleb", turned out to be largely police spin but still a generally unpleasant little fellow. Has some credentials in as much as he is a former UN Peacekeeper and has done a fair amount of work in founding some kind of social action project in Sierra Leone and Rwanda.
Yvette Cooper = Wife of Ed Balls (a leading Labour figure, I'm not that much of a fan). Hasn't really done anything terrible yet, still a figure of the Labour establishment though. Shadow Secretary for Women and Equalities.
Eric Pickles = Roly-poly Tory. Somewhat pleasing in his good-old-fashioned Toryness, basically everything you'd expect from a British Conservative. I like him for some reason. I, of course, would rather he never lead anything larger than a committee organising a village fete or something, rather than being our Secretary of State for Communities and Local Government (and doing a rather poor job at it). I would be amused to see him as a foreign secretary; he's very anti-EU indeed, god knows what he'd be like with the Americans. Almost UKIPish, except has less barely-concealed bigotry.
Jim Murphy = Terribly arrogant, soulless, dishonest, Scottish Labour, good-party-man, unprincipled, nuclear-bomb-loving, militaristic zombie. Shadow Secretary of State for Defence. The US government and the Obama administration would love him. According to US diplomatic documents leaked through Wikileaks, he led a top-secret cross party group of Unionists who attempted to block any attempts to have an independence referendum. He failed. I loathe this man with every fibre in my body.
And... that's about it.