importiworkms officenumbers
Can Numbers ’09 (part of the iWork suite) import XML files? Specifically, the format created by Excel when exporting as "XML Spreadsheet 2003."
I can't just use Excel's native format because the files are generated for our clients by a web app.
If Numbers can't handle these files, are there any other plaintext formats that could be used? I could use csv, but I would prefer to store formatting within the exported file itself.
There are two ways that an image can exist in Numbers.app, to my knowledge:
Excel doesn't support option 1.
If you drag an image file into a Numbers spreadsheet, you'll get option 1: the image will be inserted within a cell.
Instead, in Numbers, use the Insert > Choose… menu and select the image file. You'll then get option 2, which is correctly exported to .xls format in my limited testing.
I'm not sure why it's included in the export, but this is one of the default "Image Fills": 
Best Answer
Numbers ’09 supports Excel native format (.xls) but it can’t convert from an Excel XML Spreadsheet. In fact, if you rename it as “xls” and try to open it (trying to fool Numbers), you’ll probably see all the XML but not the actual spreadsheet. Which is more scary than Psychosis II back in the 80s.
Your only bet is some CVS or TEXT format, which excel can even export with Macintosh format for line endings and carrier return (if I’m not mistaken).
The big drawback is that all format and binary stuff is automagically lost in translation (certain pun intended). ;)
You’ll get the data, but not the format.
Another alternative is trying to automate the Excel XML to Excel Native format, even if your webapp outputs a XML, you could try to “transform them” before anything else.
For that, I haven’t investigated but you can start with a google query like this. There seem to be some Windows solutions, maybe something you can use/try.