ALT tags for page that has 50 similar images?

Trying to create 50+ unique ALT tags x 4000 is going to be a nightmare. Silly to have none, you're right, but having 1 for each is overkill (although it can drive more traffic if you reaaaaally want to spend that much time thinking of unique variations for each.)

If I was in your shoes, I'd take the best pictures and only tag them, as long as there's at least 1 per page, but no more than 5. (5 variations of "allen coat of arms" are easy enough, 54, not so much). But that's just me.

Tag the clearest, best looking pics of each.
"Coat of arms - Allen"
"Allen Surname Crest"
"Allen Surname Coat of Arms"
"Crest for Allen Surname"
"Coat of Arms Allen Family"

(just for some ideas). ALT tags help your images get picked up in Google Image search, so obviously the more the better, but too many similar tags on 1 page can be seen as gaming the system (bots/crawlers aren't always that smart, you know), so I'd personally stick to 5 max per page.

I noticed that you have multiple color variations for each coat of arms. Why not add in a color descriptor also like "red coat of arms allen family" or "allen family coat of arms in royal blue"?

SEO aside, the purpose of an alt tag is to help anyone who can't see the image to understand what it's all about. You would be serving that purpose as well as ranking for specific color modifiers that someone just might actually search for.

If I'm in the allen family and blue is my favorite color, it seems likely that I would search that.

You already have the answer on your webpage.

• Allen
• Allenn
• Alleyn
• Alleen
• Allein
• Allien
• Alleyne
• Allan
• Allene
• Aellen
• Alleni
• Alleon
• Aullen
• Alland
• Alan
• Allin

Traffic will search for all the name variations.

Example:

• Allen coat of arms
• Allenn coat of arms
• Alleyn coat of arms
• etc...

To be honest, alt-text is weak for SEO.

The number one ranking factor for images is the same as webpages, followed backlinks pointing directly at the file/image.

Go look at all the competitive image niches. The top ranked images all have followed backlink profiles pointing directly at the image file (ex: .jpg, .png, .gif). So, when you're serious about ranking images, start building followed links.

Now I don't expect you to build 4,000 link profiles per all the images but you do need to be figuring out your most popular crest/images and building the links.

That's how it's done.