Heroes are not infrequently to be found on horseback and horses have often featured on the covers of romances; I've posted a short piece about heroes, heroines and horses at my website. I should probably warn you that I chose the covers above purely because they include horses, not because they're attached to any of the texts I quote from in my mini-essay.
race and cover art by posting the cover of Cindy Dee's Soldier's Rescue Mission.
And re heroines in historicals, Isobel Carr has been doing a little bit of research into the ages at marriage of Georgian and Regency aristocrats:
How old were most daughters of the peerage (the most common heroines in our books) when they married for the first time? Stone’s chart shows that during the first part of the era, the median age was ~20-22. Post 1750 (correlating with the passage of Hardwicke’s Marriage Act; Coincidence?), that age jumps up to ~23-24. So, the most common age for the daughter of a peer to marry was not when she was in her teens, but when she was in her early 20s, and an unmarried twenty-five year old would not really be much of an outlier.She also discusses accurate ages for heroes at marriage elsewhere in her post.