Hi!  first of all, you have to be cleared about image, methodology and metrics in tourism branding. 

Interbrand, Brandz, and other associations have different methodologies for a brand, not just active and passive, it's about meanning in consumer, etc. World Organization Tourism certainly must have many useful information, you only have to decide, or add the things you feel important, perhaps development of infraestructure, etc.

Brand image of tourist destination  is the  impression of destination in the consumers' mind which  is developed over time through advertising campaigns with a consistent theme, and is authenticated through the consumers' direct experience. Brand image has been recognised as a key factor for consumers in selecting a destination. It is acknowledged that tourists’ selection of a holiday destination is founded on the degree to which the place generates favourable images Hence, image determines if a destination has the potential to satisfy prospective tourists. A successful brand image should transmit a message that communicates the product’s benefits, emphasize the positive features of the destination, and differentiate it from other ‘realities’ by the presentation of tangible cues. Following link may be more useful in determining the construct for the study.

ftp://ftp.repec.org/opt/ReDIF/RePEc/ibf/gjbres/gjbr-v6n1-2012/GJBR-V6N1-2012-7-revised.pdf

Destination image and destination personality (DOI 10.1108/17506180710729619)

I think this paper will help you sir.