When you set a QML image source to a string, the QUrl(const QString&) constructor gets used to convert to a QUrl property. But this uses the default "TolerantMode", which handles a hybrid of encoded and unencoded URLs. There is no way to specify a filename that actually contains the characters %20 in the name, because even though it's expecting an unencoded URL, it second guesses you if it sees those characters.

You can see this just by running qmlviewer with this sample code:

import Qt 4.7
Column {
Image

Image

}