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A: Zip them up in a flat file (no subdirectories) and upload that zip file. Tiki can handle this. Be careful: the maximum size of uploaded files has to be configured in php.ini.
A: You have PHP with GD or imagick support? If you don't know, create a php page with <?php phpinfo(); ?> in it and view it on your webserver. A page with all php and server settings should be displayed.
A: GD doesn't support GIFs due to copyright issues. This may change in some time. If you need GIF support, try imagick.