Problem is, that exhibition buildings generally have an ephemeral air- here one day, gone the next. Also, again generally, because they were intended to be temporary structures they were lightly built with a focus on prefabrication- hence why the Crystal Palace was composed primarily of iron (it could be set up and taken apart like some giant prototype meccano set). Is it this fleeting atmosphere you refer to?
Of course, the one big example of such a structure surving today would be the Eiffel Tower (1889).
For my own part, I would nominate the following as having a certain SP appeal to them:
-Paddington Station, London, 1854: Brunel's iron trainshed roofs in particular. Probably one of the most intact (ie-least interfered with) major Victorian railway termini.
-Tower Bridge, London, 1894: Iron framed bascule bridge, sheathed in a mock-Medieval facade.
-Oxford University Museum, Oxford, 1860: (mentioned above) Early major example of Ruskinian Venetian Gothic, with an emphasis on decor carried out by 'peasant workmen'. Also of note due to the iron and glass roof of the courtyard.
-Sir John Soane's House, London, stages up to 1837: A complete maze of spaces and rooms filled with momentoes of Grand Tours and architectural history. A real 'Cabinet of Curiosities'.
-Crossness Engine House, Crossness, 1851 (?): Sole surviving example of enginehouses built to pump sewage out of London. Of note due to the survival of the engines themselves and the decorated iron frame.
