many images in wikipedia are not shown. Typically some are greyed-out, and are of the form data:image/png;base64,iVBORw0KGgoAAA
Most images in wikipedia are not visible. Icons are ok. Looking at page info, the greyed-out ones are of type Background in the list and type PNG Image in the text below them.
Example:
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAALCAMAAABxsOwqAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAGBQTFRF////R2uZMmGd5rp2boqvMFyS9unUTXWr5KQ/N2mn/Pr42Jg14Zstl6a80K93XXiVooVQ57VnpLnW4a1a36ZMr7Cwgpm5PXGw78mO+O/g1t7n5Orxk6zMvMne7/Dw6+zt5K6gdAAAAAF0Uk5TAEDm2GYAAABdSURBVHheHcpFAgMxEANBDZhhmQP//2Uc90V1EICrLuti0YqnyORrbLSrWPHJ/ukn8bkzbrnVD/MwpjQOb+B2hyvbQe7BTiG8ZmYqUOLglA0rCrcJxpiCz049/f4A9ZID96SyhDEAAAAASUVORK5CYII=
versions 3.5 3.6 and 4.0.1 Debian squeeze