I would really want the File Manager window bigger. I use 4K monitors and I can barely fir 6-9 pictures to preview. There should be some setting to adjust this window size. There are way to many parameters in this little window to fit on this small size. Preferably TABS would help to fix this issue. Perhaps there is a way but I do not know it, and if there isn't this is something quite important to add. I'm a developer myself and setting a modal window size is quite easy.

/* A ratio of 16:9 */
.mceModal .mce-modal-portrait-full {
    max-width: 1440px;
    max-height: 810px;
}

Same thing for guides and lines - their colors. The light grey on white is absolutely unacceptable.

.wf-column {
    border-color: #888;
}