If here is an image on my T-shirt, like how polo T-shirts has the image of a horse, but the image is not clear and only shaded in black, can one perform Salah while wearing this T-shirt?
If the image is not clear, just as was mentioned by the questioner, then it is permissible to perform Salah in this T-shirt, otherwise it is disliked and should be avoided.
کما فی تکملۃ فتح الملہم: والحاصل ان تصاویر الحیوانات تحرم اجماعًا ان کانت کاملۃ لہا ظل مما یطول استمرارہ بخلاف ناقص عضو لا یعیش بہ لو کان حیوانًا۔ (ج۴، ص۱۵۹) واللہ اعلم بالصواب