Besides dust prevention, the role of that io shield is to make good contact between the connectors and the computer case, and basically improve the ESD protection (electro static discharge). When you plug things in back connectors your skin may be statically charged from walking on the carpet (or just from rubbing clothes against your skin) so if you touch contacts with your fingers you may zap them. The exterior of usb connectors and other connectors is usually grounded but it doesn't hurt to have a shield there and increase the chances your fingers will hit the shield first.. and the shield is connected to the metal of the case, which is grounded through the power supply so everyone's happy.
Anyway, it's a minimal risk, and can often be ignored.
The io shield also completes a sort of Faraday cage, basically blocks (or reduces) electromagnetic radiation from various components in your computer from affecting unshielded cables (the audio cable of your speakers sometimes, depending on the quality of the speakers), your vga cable... digital cables like hdmi or displayport are less sensitive and usually shielded, and others like usb have some shielding built in... Also blocks EMI from affecting various radio devices (AM radio in the same room etc, if you're really unlucky you could try to tune into an AM station and you'd hear buzzing or whining over the radio station)
So if you don't care about all of these, sure, you can install a motherboard with io shield. Just wanted to explain that it's not just something visual, to please you estethically, there's more purposes for the shield besides beautification.