Here's some lo-resolution screengrabs from my camcorder of my 2006 yard haunt. It shows some indirect shots of my entry archway I built at the last minute similiar to what you're thinking about:
PHOTOBUCKET GALLERY LINK
I had more video frames showing ToT's in white costumes & wigs glowing underneath the archway and a close-up of the roof inside but I'd have to go back and recapture the video which I'm not going to do anytime soon but you get the idea from these. I'd add another 24" blacklight bolt to the roof for more of an effect. I tied jute twine around the flourescent tube just in case it might pop out but it was fine.
The way I put it up was to put the roof together then set it on the ground where it would be then marked the 4 corners with the rebar then pounded the rebar into the ground then twisted the 4 vertical PVC corners into the ground then lifted the assembled roof onto them then pressure fit the roof to the vertical posts.
If I wanted to make it go all the way back to the house I'd just add another section or pull this one apart and add some PVC Tees to connect the two but two separate sections would be a lot easier to put up and take down for what it is. But I only have storage space for this section and it did the trick.
ROUGH SPECS
7 ft tall total height
6 ft tall to the crossbrace
4ft 6 in wide to stradle a 4 ft walkway
5 ft 6 in deep
2ft long rebar in ground in corners
FRAME
(14) 1in dia PVC Tee - Home Depot
(8) 1in dia PVC 45 elbow - Home Depot
(8) 1in dia PVC x 10ft lengths to cut - Home Depot
(1) PVC cutters - Home Depot
(2) cans Krylon Fusion Ultra Flat Camo Black Spraypaint - Walmart
(1) Paint respirator - Home Depot
(1) electrical drill
(1) philips screwdriver
(mult) No.8 wood screws - Walmart
To screw the roof pieces together
Note: The roof PVC is pressure fit onto the four vertical peices
ROOF
(1) 3ft x 120ft Black Weed Proof Plus - Walmart
(1) 4oz ClearNeon UV paint white - Alan at Quantum Leap Unlimited
(2) 1in foam paint brushes - Walmart
(2) 2in foam paint brushes - Walmart
To paint UV dots on underside of roof
(1 or 2) 24in blacklight fluorescent bolt - Walmart
To light white sheet strips and UV paint dots and any white ToT costumes and wigs that pass thru
SIDES
(1) Full white bedsheet cut into 3" wide strips - Walmart
Loop the strips around the PVC and staple
(1) stapler
Cut the lengths or fold up to desired lenght and staple
SKULL STROBE ON FRONT
(1) plastic skull strobe light -Walmart
(1) roll rebar tie wire - Home Depot
To hang skull by threading thru the skull and tie to the PVC
(1) black hook for skull strobe light - Walmart
To hold the electrical cord
OTHER
(1) extension cord taped up to roof
For blacklight plug
NEXT YEAR SOUND
(1) iPod Shuffle with music and sound FX from my CD collection into iTunes
(1) DLO iPod Shuffle Action Jacket
Velcro wrapped around PVC roof piece
(1) Set of Altec Lansing computer speakers - Walmart
Secured to PVC frame with rebar tie wire