Zhe,
This is all about the size and number of your images. SVG and icons usually don't add much, if you use photos, png jpeg compressed images and keep their size down you can go a long way.
However it all depends on if its single file wiki, or node version or if you can use the method to externalise them (via canonical URL) or use skinny tiddlers, and how many you include.
Tiddlywiki can handle large volumes of images but you have to implement it according to the volume and size of YOUR images. This is also unavoidable on any website.
Regards
Tony