Yum update is done during build means as of last week updates to Oracle Linux 7.4 .

Bigger issue:
Virtualbox has an issue full virtual desktop resize issue, option greyed out with Oracle Linux 7.4 which is reported fixed in 5.1.x (5.1.27 Testbuild) did not work for me on my mac: https://forums.virtualbox.org/viewtopic.php?f=15&t=84201

Smaller issue - big icons try:
gsettings set org.gnome.nautilus.icon-view default-zoom-level small
early in the build - if not in gnome do:
dbus-launch gsettings set org.gnome.nautilus.icon-view default-zoom-level small

[Same issue will happen if you run yum update (or it auto runs somehow) on an existing Oracle Linux 7 VM - like a previous Oracle developer day VM]