Where are you trying to download iDVD 7.0.4 application? You need to get it from an iLife disk which has been discontinued. However, if you can get an iLife 09 or 11 disk from Amazon.com or eBay.com you'll be able to install iDVD 7.0 for 7.1 and then upgrade it to 7.0.4 via the updaters from the Apple Download page: Apple - Support - Downloads.
All older themes from V1 thru V5 can be downloaded via this link: http://swcdn.apple.com/content/downloads/53/06/031-11609/gethaqto8acx9pvblr4pnhi tssanvhtpiz/iDVDExtraContent.pkg
Note: the link above will begin the download of the Contents of iDVDExteraContent.pkg install package.

However, iDVD 7 does not work very well with High Sierra. You might be better served trying out the DVD Maker Lite - DVD Creator app from the App Store. There is a free demo version that you can try out to see if you like it before purchasing the full version. The demo version puts a watermark on the video output.
This app had a number of themes and can create video DVDs from still photos or video files like iDVD can. It's not nearly as intuitive as iDVD is but is 64 bit compliant and will continue to work with future OS X systems.
