Just a word of caution - remember to check your ancestry user agreement and any copyrights before you download sources and upload them here :D There have been a number of discussions on this issue, and here are links to just a couple:
I am not an Ancestry user, but if I recall Ancestry will in many cases provide a 'proper' citation on-screen which can be copy/pasted where the downloaded GEDCOM reference is often full of additional "fluff" that makes the citation awkward to read. It would be realtively simple to add "cited by ancestry.com" or "[digital image], Ancestry.com" to give appropraite credit to the repository.
The important thing is that any citation clearly indicates what ACTUAL source is being cited - if, as an example a citation is for a specific page of a census for a specific town, county, state I can look up the info through other repositories even if your link points to an ancestry image that I cannot access.
Many wikitree people also place little to no value on user-trees (from ancestry, familysearch, etc) as a source as they are often not well documented, and in many cases full of errors, duplication, and conjecture. This is not to say wikitree doesn't have the same problem, but at least here we are making an effort to limit and fix the problem.