Steve Milne sent me a copy, and a pdf, of his "Infinite Families of Exact Sums of Squares Formulas, Jacobi Elliptic Functions, Continued Fractions, and Schur Functions" which is an entire issue of The Ramanujan Journal: vol. 6, no. 1, March 2002. There is also a two-page preface by George Andrews. I admit, the main focus is dimension $4 n^2$ or $ 4 ( n^2 + n).$ But at 143 pages and 259 references, there might be something you like. Email me if you would like  the pdf, it is not obvious to me that there was implied permission for me  to post it on any websites. 

EDIT, Monday 7 June:

Robin Chapman mentions the papers on odd numbers of squares by Shaun Cooper, some previews at

http://www.springerlink.com/content/w1w160424g78284l/ 

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WKD-49M0N15-2&_user=10&_coverDate=12%2F31%2F2003&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1361799989&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=06e65462261642a34cd15f855b170ef0 

and this is the guy:
http://www.massey.ac.nz/~wwiims/people/s.cooper/ 


and Roland Bacher mentions a Bodo Lass paper which has got to be more or less the same as this arXiv piece

http://arxiv.org/abs/math/0507144 

I'm not sure about the etiquette in general of incorporating comments (i.e. the effort of others) into my "answer," but in this case Dror would not automatically be notified about said comments owing to their location, while he would be notified about comments directly under his question. And I don't see that he has noticed these new references.