As I recall the SU blog runs on wordpress, and I was using windows live writer to post on it. Its part of windows essentials, works with WP blogs and if I recall correctly did/does most of what you have listed there 


Start a new post while offline - yes
Lets me edit posts I created already with the program yes (though I can't remember if it edits uploaded posts)
Spell check - and grammar check
Uploads new posts when I reconnect - yes
Has the same features as the online editor (i.e. toolbars, WYSIWYG and Code editor)kind of - it has its own UI but its broadly compatible and in some ways better
Free (as in beer) yes
Works on either Windows or Mac OSX - windows only


Offline WordPress post editor/creator
The code I'm using is this one 

background: url(bilder/cover.jpg) no-repeat center center fixed; 
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}


What I'd like to accomplish is that the background image is changed after like 2 sec to a background image that then stays put.

I know there are Jqueries for changing backgrounds like this but I'm not sure how to make something like that work with the code I'm using! It would be awesome if someone hade a solution to this!

My starting point for changing background was the code I found on w3schools:

{
width:100px;
height:100px;
background:red;
animation:myfirst 5s;
-webkit-animation:myfirst 5s; /* Safari and Chrome */
}

@keyframes myfirst
{
from {background:red;}
to {background:yellow;}
}

@-webkit-keyframes myfirst /* Safari and Chrome */
{
from {background:red;}
to {background:yellow;}
}

