support for .svg images ?

As you are unable to import the svg's I would guess that they are not supported. iPhoto is geared firmly at the photographer.

If you want feature enhancements: iPhoto menu -> Provide iPhoto Feedback

However I would not expect such enhancements to iPhoto 08 which is now supplanted by 09.

Regards

TD

Welcome to the Apple Discussions. The iLife applications do not support the scalable vector graphic format. You will need to convert to one of the image formats that is supported: JPEG, TIFF, PSD, GIF and PNG.

TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto (iPhoto.Library for iPhoto 5 and earlier versions) database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've created an Automator workflow application (requires Tiger or later), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. There are versions that are compatible with iPhoto 5, 6, 7 and 8 libraries and Tiger and Leopard. Just put the application in the Dock and click on it whenever you want to backup the dB file. iPhoto does not have to be closed to run the application, just idle. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.

NOTE: The new rebuild option in iPhoto 09 (v. 8.0.2), Rebuild the iPhoto Library Database from automatic backup" makes this tip obsolete.

SVG is a resolution independent vector image format much like stuff created with an application such as Adobe Illustrator.

iPhoto only deals with pixel-based images, but you can convert SVGs.
With the SVG open in Safari choose File > Print and in the dialogue box PDF > Save PDF to iPhoto. That will render a pixel image and place it into your iPhoto library.