You cannot modify the colours of a linked image and have Word retain them. Any time the field updates (e.g. when you do a print preview or print the document), the images will revert to their original colours. Accordingly, any changes of that kind need to be made to the original image - or don't link to it.
If you want to constrain the image sizes, insert them into table cells with a fixed column-width and row height:
• For the rows, set the exact row height under Table Tools>Layout>Properties>Row>Specify Height>Exactly.
• For the columns, set the preferred column width under Table Tools>Layout>Properties>Columns and uncheck the 'automatically resize to fit contents' option under Table Tools>Layout>Properties>Table>Options.
As for your captions, they're best associated with the images by using a two-row table, with the image on one row and the caption on the other. I've posted macros here for automating that process.
I note that you have cross-posted the same question at:
http://answers.microsoft.com/en-us/o...c-cb29b67d96a0
For cross-posting etiquette, please read:
http://www.excelguru.ca/content.php?184