I'd get the rug and cut the hole in it. remove the vent cover and put that on top of the rug. It should blend in and work perfectly. No reason not to have a hole in the rug but I guess it could be a pain to clean under it.

Like you said a vent cover is fine.

Wait...not crazy about having a cut out in an accent rug. A carpet, yes, but I think it would look really weird on a small accent rug. Was just asking if it would be safe to cover it (not a fire hazard). My options are slightly smaller rug than what is there, so as to not cover the vent, or to cover it completely with a rug the width of the side door panels and be able to go larger. Sorry if I didn't make that clear.

Most vents have a little adjuster attached that allows you to close off the register. You could do that, assuming you have one (if not, you can easily pick up a replacement at big box store. Make sure you measure for your replacement though, as they do come in different sizes. Your air will then be rerouted to the next nearest vent and you wont have to worry about it. Cover away. =)

You could do a large circular rug to break up the squareness and it might then allow room for vent

I put a big bamboo area rug in our foyer right on top of the closed vent with no issues or problems. If you don't need the heat cover away!

Thanks for all your help. We do have a vent cover where we can close it off but I wasn't sure if for fire hazard reasons, if this was enough if a rug covered the entire vent, so I thought the magnetic cover would just be extra protection. I want the width of the rug because right now, people walk in the front door and need to stand on this tiny mat to wipe their feet. And, since I wouldn't want anything asymmetrical, I want the rug to go wide on the other side where the vent is. Circular would look nice but I'd like the rug to wipe feet on as people walk in (we do not have a covered front porch). I do want a larger rug, maybe going all the way to the stairs would be nice, depending on rug sizes. Really need a patterned rug that can get dirt on it from shoes! Just really was concerned about the heat trapped under the rug being a fire hazard.

I was once advised not to cover up the vents by a HVAC expert. The closed vent forces the air back to the fan thus creating pressure, and ultimately problems with the heater etc. The issue came up because my furnace went off and when researching why, it is because I had quite a few vents closed out because my family was out of town for a month. The expert advised me not to close even 1 vent, because the HVAC channels are not designed to distribute the blocked air, they are designed for only 1 way air flow.

So long story short, I would recommend to try and not cover the vent.

I wouldn't close or cover the vent. It will mess with your HVAC system's balance. Do what deco suggested above so you don't cover the vent. Here is a link that explains it a little better http://www.amgableheatingandcooling.com/id16.html

I also have this exact same situation in my front entry. My heat vent has a wood cover...does anyone have pics of rugs they've used in situations like the one pictured above