Faut plafond en velum (COTON GRATE) blanc. - Un rail de 3 spots. - La moquette au sol de couleur chocolat - 1 enseigne banderole en forex avec le nom ...
www.cdo-events.com/fr/e_archi.php?id_men=2&id_s=4&s=088ad05...

Plafond vélum décoratif de couleur. Decorative coloured AWNING CEILING. sur colonne enseigne. on sign column. Eclairage. Lighting ...
www.batimat.com/pdf/plaq_stand_07_light.pdf

Soften a ceiling by attaching a FABRIC AWNING with scalloped edges.
http://www.hgtv.com/hgtv/dc_design_small_space/article/0,179...

Brand Name: The Vellum Ceiling Dressing Range Colours Available: 13 variants of colour & textures
Product Type and Applications:
Specialist Material for ceiling dressings over exhibition stands, displays, marquees etc.
Fire Rated to M1.
http://www.ctn-uk.com/vellum-ceiling.htm

BUT:
CTN is HEADQUARTERED IN FRANCE, and has companies in Belgium, Spain and the UK, with more locations planned.
CTN Exhibitions Ltd. is part of the European CTN Group of companies specialising in the supply OF FLOOR AND WALL COVERINGS to the EXHIBITION, EVENT, DISPLAY AND CONFERENCE MARKETS
http://www.ctn-uk.com/

15,000 ghits for "fabric ceiling", on the other hand!

Given the similarity of the type of show and the business of The Vellum Ceiling Dressing Company, I might actually be tempted to call it a vellum ceiling ...


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Note added at 7 hrs (2007-08-31 16:51:58 GMT)
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Re. "ajouré", that's a good question. Really we need to know if it's "velum ajouré" or "plafond (en velum) ajouré". [I've just noticed, BTW, that it's "Velum" with a capital V in your text, which would seem it suggest it might be the brand name]. If "velum ajouré" then Françis' "openwork" is as good as anything. If "plafon ajouré", it might be what is called an "open-cell ceiling", though. This is those false ceilings made from intersecting slats of metal or plastic on edge, forming an "eggcrate" effect (these ceilings are also known as eggcrate ceilings . If you stand directly beneath a "cell" and look up, you can see in the plenum above (which is usually painted black, so you can't actually see anything). I suppose there is no reason why the same should not be done with strips of fabric.