• Animated GIFs can be added just like any image
• For web3d can you provide some pointers
• For flash you can use the following code

#\set($\width = "500")
#\set($\height= "500")
#\set($\flashurl = $\doc.getAttachmentURL("filename.swf", "download"))
#\includeForm("xwiki:XWiki.Flash")

You can also replace the call to getAttachmentURL with and http:// url..

The next XWiki version will provide an even simplier macro for this.