It's best practice to try to identify whether media will need to be versioned ahead of time. If you know media is going to need to be versioned based on language, you should make sure to update in your web.config the following attribute:
<!--By default, Media items are not versionable and the below setting is set to false in the web.config.
If you upload an image in one language, it will persist across all language versions.
If you change this to true, then versioning will apply and you would have to set the media item into all language versions,
or enable fallback, but if enforce version presence is turned on and media template guids are included in EnforceVersionPresenceTemplates,
then you'll have to make sure all language versions at least exist-->
<setting name="Media.UploadAsVersionableByDefault">
<patch:attribute name="value">true</patch:attribute>
</setting>
Alex Shyba's Partial Language Fallback module will successfully work with this. I would recommend making sure not to enforce version presence on any media templates (don't want to force admins to have to create blank language versions). Then they can create english versions and then only create a language version when they need to override it.
You will need, in the case of using partial language fallback, to make sure the enable fallback checkboxes are checked on the media versionable template fields.
I also recommend updating the media provider so that it embeds language into the media url so that caching doesn't come into play. EG: if you create a pdf named Directions.pdf and it loads at www.site.com/media/Directions.pdf, when you switch between languages, it very well could cache it. So you would want to update the media provider to encode the media url with the context language.
You can see a demo here:
https://github.com/Verndale-Corp/Sitecore-Fallback-FullDemo
public class CustomMediaProvider : MediaProvider
{
public override string GetMediaUrl(MediaItem item, MediaUrlOptions options)
{
Assert.ArgumentNotNull((object)item, "item");
Assert.ArgumentNotNull((object)options, "options");
string result = base.GetMediaUrl(item, options);
// Added by Verndale, check if language should be embedded
UrlOptions urlOptions = UrlOptions.DefaultOptions;
urlOptions = LanguageHelper.CheckOverrideLanguageEmbedding(urlOptions);
if (urlOptions.LanguageEmbedding == LanguageEmbedding.Always && options.UseItemPath)
{
result = "/" + Sitecore.Context.Language.Name.ToLowerInvariant() + Sitecore.StringUtil.EnsurePrefix('/', result);
}
return result;
}
public static UrlOptions CheckOverrideLanguageEmbedding(UrlOptions urlOptions)
{
var thisSite = Sitecore.Context.Site;
if (urlOptions.Site != null)
thisSite = urlOptions.Site;
if (!String.IsNullOrEmpty(thisSite.SiteInfo.Properties["languageEmbedding"]))
{
if (thisSite.SiteInfo.Properties["languageEmbedding"].ToLower() == "never")
urlOptions.LanguageEmbedding = LanguageEmbedding.Never;
else if (thisSite.SiteInfo.Properties["languageEmbedding"].ToLower() == "always")
urlOptions.LanguageEmbedding = LanguageEmbedding.Always;
else if (thisSite.SiteInfo.Properties["languageEmbedding"].ToLower() == "asneeded")
urlOptions.LanguageEmbedding = LanguageEmbedding.AsNeeded;
}
return urlOptions;
}
}