For any of my hand painted portrait items, I need a CLEAR, WELL LIT and GOOD QUALITY reference photograph to work from.
Perhaps my best tip is to remember that I do not know your horse/pet. Likely I have never even seen them! I can only paint what I can see, so choose a photo that shows your horse not just at a flattering angle, but in a way that shows their personality too. An alert, happy expression with an open eye is likely to guarantee a much closer resemblance to your horse than one of them half asleep, or with their ‘work face’ on.
For horses, a three quarter profile works best (side on is also fine, but will not show markings on the front of the face). This is often the most flattering angle as well as allowing your horse’s individual markings to be shown. Front-on photos generally do not work well – except in the rarest of cases, even the most handsome horse ends up looking like a donkey from this angle!
Most modern smartphones are able to take photos in suitably high resolution – just check they do not get compressed and lose quality on sending! Original photos are always best but I can and have worked from poorer quality e.g. Facebook screenshots in the past, especially when photo options are limited such as for a horse who has passed away but please remember, the clearer the photo, the better the painting! In particular the eye needs to be very clear, this is what most captures your horse’s personality.
Ideally the photo will be taken from the same height as the horse to maintain the right perspective. The subject should fill the frame as much as possible – I am painting a headshot, a distant photo of your horse in the field is very little help! Photos can of course be cropped, but if too distant they will lack the detail required to produce an accurate likeness.
Outdoor photos are best, but try to avoid taking photos on very sunny days – such harsh lighting often distorts natural colours, as well as creating difficult highlights and deep shadowed areas. A bright but cloudy day is often best.
If your horse is an unusual colour, it helps to send me more than one photo, and if your best photos are not representative of your horse’s true colour (for example, a clipped coat, roan, a black horse that looks bay/brown in the sun etc) then do talk to me about the colour your horse actually is, so I can try to match it as closely as possible (bearing in mind the limitations of paint compared to nature’s beauty!)
Generally I paint without any tack (bridle/headcollars etc) I am happy to paint from photos where they are wearing tack, and remove tack as part of the painting process (many people choose this if the horse is wearing a headcollar, for example) but obviously this does mean a degree of guesswork if the tack is obscuring key details such as markings – again multiple photos can help.
If you are unsure if your photo is suitable then please feel free to send it to me before ordering to check and I can advise – or if you send me multiple photos I can choose the best one.

I have recently started painting dogs as well as horses, and the same guidelines generally apply. Dogs are more forgiving from a front-on perspective, than horses, but still ideally need to be taken from their height. With horses you may need to stand on something to get a good photos – with dogs you may need to get down on the floor!
Again ideally you want an alert, happy expression – but note that large tongues lolling out often detract from a portrait.
As I am less experienced with dogs, a selection of photos rather than just one is very helpful.
As always, I am happy for you to send me photos before committing to an item, and we can discuss whether any/one will work, or I can make suggestions based on the photos you send.

This is a useful blog with 9 Pet Photography Tips (digital-photography-school.com) to help you get the best photos of your horse or pet.