I was planning on giving user an option to upload files while answering a survey. Is it possible to attach an item to a survey list ?
This may not be an ideal answer; but since surveys are not easily customizable, and a custom list doesn't behave exactly like a survey, you might try this:
In SharePoint 2013, you can select the External Data type to specify what types of files you want to upload when you create each question. The hitch is that your administrator has to have enabled External Content Types or you will not have permissions to create an upload feature as part of the survey.